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THE
VELIGER
A Quarterly published by
CALIFORNIA MALACOZOOLOGICAL SOCIETY, INC.
Berkeley, California
R. Stohler, Founding Editor
Volume 26
July 1, 1983 to April 2, 1984
TABLE of CONTENTS
Number 1 (1 July 1983)
Our thanks to Rudolf Stohler.
R. I. SMITH
New molluscan species (Gastropoda: Neogastropoda) from
the tropical eastern Pacific.
LEROY H. POORMAN
The biology of the northeastern Pacific Turridae. III. The
habitat and diet of Kurtziella plumbea (Hinds, 1843).
R. L. SHIMEK 10
Flow through and around the abalone Haliotis kamtschat-
kana.
ASNIGEBVIOUMZOW! Gigah cee oo as ke neil ee es 18
Shell strength in Corbicula sp. (Bivalvia: Corbiculidae)
from the Potomac River, Maryland.
VicTOR S. KENNEDY AND JAY A. BLUNDON .... 22
Relationship between beak morphometrics and live wet
weight of the giant Pacific octopus, Octopus dofleini
martini (Wilker).
SHAWN M. C. ROBINSON AND E. BRIAN HARTWICK . .
v6. a0. aa Os ed faked op ad ce Sra ne ee 26
Studies on the reproductive biology of some prosobranchs
from the coast of Pakistan bordering the northern
Arabian Sea. II. Egg capsules and larvae of four
species of Thais.
SOHAIL BARKATI AND MUZAMMIL AHMED 30
Comparison of northern and southern populations of Ep-
itonium tinctum (Carpenter, 1864) on the California
coast.
CaREY RESCH SMITH AND AMY BREYER 37
The reproductive cycle of the trochid gastropod Oxystele
variegata (Anton, 1839).
M. A. P. JoskA AND G. M. BRANCH.......... 47
The larval biology of Brachidontes modiolus (Linné, 1767)
(Bivalvia: Mytilidae).
ANGELA FIELDS AND EUNA MOoRE 52
A comparison of the species richness and trophic roles of
gastropods and chitons on rocky shores of temperate
and tropical west America.
ENILNN (Gi, IMOTUUTY slog ao soe ooudvianoay ooo gesn 62
Range extensions of three opisthobranch mollusks to the
San Diego—La Jolla (California) Ecological Re-
serve.
Hans BERTSCH AND TOM SMITH.............
Number 2 (3 October 1983)
Radular patterns, systematics, diversity, and ecology of
deep-sea limpets.
CAR OUEBS MENCKMANE ane ceisc lair s skeen 73
Additions to the opisthobranch mollusk fauna of Marin
County, California, with notes on the biology of cer-
tain species.
WILLIAM B. JAECKLE 93
Specialized feeding in mitrid gastropods: evidence from a
temperate species, Mitra idae Melvill.
ALLAN FUKUYAMA AND JAMES NYBAKKEN...... 96
Homing in the West Indian chiton Acanthopleura granu-
lata Gmelin, 1791.
DAVID ENT OOK eee ecieib ye Actin ssh nd alee eens 101
Aspects of reproduction in some enoploteuthid squids from
Hawaiian waters.
LIGA IME, JE\OW CSI vers bao os om Oe gee ome oe 106
Shell repair frequencies of two intertidal gastropods from
northern California: microhabitat differences.
A ONATHANEBS GBLELERMM a ae ane aor lS
Morphological divergence and predator-induced shell re-
il
pair in Alia carinata (Gastropoda: Prosobranchia).
Jutta BERGMAN, JONATHAN B. GELLER, AND VICTOR
CHOWMAAE fasts ee eee EAE Nes cements 116
Thermal effects on some mangrove mollusks.
Honc Woo KHOoo AND ELEANOR CHIN ....... 119
Barnacle attachment on live Nautilus: implications for
Nautilus growth rate.
NeIL H. LANDMAN 124
Distribution and abundance of Caecum cornucopiae (Gas-
tropoda: Prosobranchia) on Cladophora crystallina mats
in a Bahamian salt water lake.
BESTS YD) Aas ape erates Mak pre Soterek ee, fy seal kee geet 128
The Bermudan and Caribbean sacoglossan mollusk Elysia
flava Verrill now recorded from the Greek Aegean
Sea.
PIE H OMPSON Per pea ceva oocytes ae 136
Do oystercatchers influence limpet shell shape?
P. A. R. Hockey aNnD G. M. BRANCH ........ 139
A range extension of Nassarius miser (Dall, 1908).
IROBERM Iss EIOWLEY arse as) terior Shee oer 142
Number 3 (3 January 1984)
Activity, dispersion, and size of Lanistes nyassanus and L.
solidus (Gastropoda, Ampullariidae) over the depth
gradient at Cape Maclear, Lake Malawi, Africa.
S. M. Loupba, K. R. McKaye, T. D. KOCHER, AND C.
J SSTACKHOUSE snot ee eee 145
The Recent Crassatellinae of the eastern Pacific, with
some notes on Crassinella.
EUGENE COAN 153
Description of five new species of Hawaiian Eulimidae.
ANDERS WAREN, BEATRICE L. BURCH, AND THOMAS
A. BURCH 170
A new species of Ischnochiton (Mollusca: Polyplacophora)
in the Gulf of California.
ANNINONNO) JJo JONNY, 6 occ 0cso0ccv0ss00as oc 179
Records of Cuthona pustulata (Alder & Hancock, 1854)
from the Canadian Pacific.
TERRENCE M. GOSLINER AND SANDRA V. MILLEN...
Ee Ae eee eee ey ernest PY chats, Sh ga 183
The ecology of Parvilucina tenuisculpta (Carpenter, 1864)
(Bivalvia: Lucinidae) on the southern California bor-
derland.
GILBERT F. JONES AND BRUCE E. THOMPSON... 188
Hybridization of two populations of a marine opistho-
branch with different developmental patterns.
HiLitary H. WEstT, JUNE F. HARRIGAN, AND SIDNEY
K.. PIERCE. ..< 250. 409505005500 ee 199
The opisthobranch mollusks of Humboldt County, Cali-
fornia.
WILLIAM BS JJAECKILES 35 a0 6 ooo eee 207
Doridacean nudibranchs from Sri Lanka, with descrip-
tions of four new species.
NATHALIE YONOW 214
Technique for narcotizing and fixing veliger larvae of Am-
phibola crenata.
PENNY STIRLING, COLIN LITTLE, MARGARET C. PIL-
Number 4 (2 April 1984)
Supplementary information on the morphology of Phes-
tilla melanobranchia Bergh, 1874, from Seto, Ki,
Middle Japan (Nudibranchia: Aeolidacea: Tergipe-
didae).
ISIKUMARO BAB AGS a5 o/c cae Oise ey ais ee era ee 241
Distributional records for terrestrial and freshwater Mol-
lusca of the Cascade and Coast ranges, Oregon.
BRANLEY ALLAN BRANSON AND ROGERS MACGOWAN
BRANSONEY a Potton ye eae eee ene ee 248
The biology of the northeastern Pacific Turridae. IV. Shell
morphology and sexual dimorphism in Aforia circi-
nata (Dall, 1873).
IROINIALID) Ik, SIBUIMIDK occ ounscc vende ceuccsve ce 258
Distribution and radular morphology of various nudi-
branchs (Gastropoda: Opisthobranchia) from the Gulf
of California, Mexico.
Hans BERTSCH AND ALEX KERSTITCH ........ 264
The diets of Alaskan Neptunea.
IRONALEDEIL SHIMEK@s ay Athy score ee eee yak
Spatial distribution of three species of bivalves on an, in-
tertidal flat: the interaction of life-history strategy with
predation and disturbance.
Mark L. BOTTON 282
Orientational and anatomical trends related to detorsion
among prosobranch gastropods.
1V
KINGTON, AND JOHN B. PILKINGTON....... 229
New species of northeast Pacific archaeogastropods.
JAMESTEIRI MICIZRAN Ia Aen eee eee 233
Louis F. GAINEY, JR. AND CHARLES R. STASEK .....
uygiey sao ee a ee ae ee 288
Reproductive cycle of Anomia simplex (Pelecypoda: Ano-
miidae) from Cape Cod, Massachusetts.
DD IANED py BROUSSEAU Se eee 299
Influence of varying oxygen tension on the oxygen con-
sumption of the freshwater mussel Lamellidens mar-
ginalis (Lamarck) and its relation to body size.
V. Mapan Mouan Das aNnp S. A. 'T. VENKATACHARI 305
Gaimardia bahamondei, spec. nov., from central Chile
(Mollusca: Bivalvia: Cyamiidae: Gaimardiinae).
CECILIA OsoRIO R. AND PaTRICK M. ARNAUD .. 311
Egg masses and larvae of three species of Cerithium from
the Arabian Sea.
SOHAIL BARKATI AND MUZAMMIL AHMED 316
Male reproductive system of Chorus giganteus (Lesson,
1829) (Muricidae: Prosobranchia): anatomical and
histological description.
MartTaA AMin V., IRENE LEPEZ G., OSCAR Marin S.,
ASNID) IMUASTA, IDISIUAIN| Na op oc op uve as eeaace 320
Anesthetic methods for the moon snail Polinices lewrsit.
GEORGE B. BOURNE 327
An earlier name for Nassarius corpulentus (C. B. Adams,
1852).
RICHARD E. PETIT
AUTHOR INDEX
TIMID DNAS eerie ocr os Pe oo Aa eRe 30, 316
ENINSTONT,, Wo HINA Li ie Viet clea: eh Sn Bec a 320
AARRINUNTUID),: 12, JNA latounir te ene ete etna ota euoica a penen (cess mene 311
IBVAIBVA, UEC V2 Gralla et Rete: 6 SISGUrt non ee dice ree anes tae ar sere wueme 241
TBYAIRIRATI Ls Sig aks See Gace Been cee uence Gkencnc trie atone 30, 316
{BUST GINAUAINYS »| feaulnana eate-cnel es come tre ook ve ais yee teeanee nae 116
IBERINSCHA@EAR te me cass Ga whe eile taunts ocr 69, 264
BEWUNDONNG EY ACur Minty Sr arhees rn seein dd Sts 22
TBXOVITUROINT: NA La ya! oa ed a ees ee se eo 282
BOW CHER MMO M VIR Kin natin eater ein Wan Ae, he ae 106
BOURNE GB ges uaricih te ccttsurset tats ertla arava as 327
IBRANGHRE GINS, ey aiaccsn hoists ah os i Gaele dt 47, 139
BRANSON Dy ACH wa res ert 1a Aatiny a Js coma canes 248
IRAN © Neg Rem Lenraitre efits Sie ic telecine ele wes alia a 248
[BURTOWZTAIR, ANH al cece al RU ere Sere Be oe 37
BROUSSHAUS DEA Parents, welathacsiee a cuee sie sis en 3 299
WRC HBB olen tes ene eA eee 5 ole ee ues dodrsee sh 170
BWR CAME Ata Sle eGo auieie ts betes aon ana sa.s 170
(CRETE re ey tr oy OUR E A Gone UM eee Sena 119
(CHBIONY, Ws. a2: Bead eves rele Cone ee en ear 116
GOANRIE ee ee BA eae eee HS ti were oc 153, (232)
IDAS, Wo IMIGUNG ei coereed aronetero nao tose chers cieeenet een 305
ID VAST, 1B)s: -o:ni bs abekor Ba siceeelee Seo E karen ceca enya ete tr aetna ean 128
1D) IARING ACMI ane enn inie sepcrtuneiaeneene hese atime oa os 320
HE RRETRA Nees mle Wart auer cnet aici Sei tis marek ei ss 179
IESIEVIATS) SMe Nagata ewes erent ere A ans 2 lieve tele, thio es os 52
TEAUIKSUWAN TA Nets str hee H Sety ie coe hese seg laneadg a 96
(GlATINTBN Ys, Las. 1 Be | RS" Soe) cepscltts ata Sache ciy oes tect le pane mre 288
(GIBILILIBIN | [o-IB3s ace chetonee eiguses ee encioe ae ecercaetaar™ 113, 116
(GOSTEINE Realy VIR es oe hu eons Hb koa lara eee 183
TRUATRIRIIGYAINT, - [ic] Se oe toa as basics ot aie Serer eee Sea ra 199
VARGA WiC Keen eta sleet Pyne eeu nese eset a ge ees eres = a 26
TEUIGRIMUNING: (Canty eck Sig co basics sare ok to Sen ee a ee W®
VEU OGT RING) A) Re 139
LO WBE Ag Ee ed losin Sanu en cv terge CAN Sc ee hs 142
ASE CPE SAV VES Suir seer eictia ea che eectien: 93, 207
JOINTS, Gis TESTES axe choo Gola a eRe meee ene ae ne 188
A OSIKACEIN TEE Ace 2 sapere neta ara eases Sah ls Cl vate a8 47
TRANOOTESTS 7-91 De, lg eN is a Neer a ee ee (144)
ISBNNEDYAIVES ont tie e ene is Bn deen Aa aa 22
IGERSMI CH SA oan came ase eaa Roetmionce ahs 2 264
IRHT OO SELES VN oie an Me een EMRE SE ie, ou thc et ied 199
IS @ CEE Route SO) 0 ears ell eee i aie gear Say ey By als 145
TEIN NUAIN Nea alison pera aitor creer ir Puree teor one ba cies 124
P74 G5. he en soe RS eres We eR vn Ho see 320
ISINDBERG wD RAGE aan ecauarir ity ses croes (334)
TE TATeIGTA By OM ee ar ei oie Meee tee ees Ome eyes 229
TEOWD ALS NIG Cee ee ais wep oe eemuage eee MEMES ta ci ncee etn 145
INIVARITING St ©) sete cle ea as Rah a ge are ag ane a 320
IVI CIGARS RGe gio eee Soi rare ree a Nee ys 145
IMICIERAINGS Je bleu aiy) amen mec ten eon pasar casa nea 233
INAITTEICE: NERS 5 Weare cc miteee ts, maa tied cece eS ECs tare ePaee. 6 183
IMITTETIGE RE ACR Gin tee ae eins ore sash vee enare ns Ces Poe nto wrens 62
INALGYG) S155) B Yes een Ry ear eta Ran dR tl nie, th ntoN nl aac eH eter 101
INTOORE Bes ele Cer se entrar Np eReni gts, Ry we Weta beaters 52
INVIBAKIKENS Ji tas rosenusyoibae e mascara cae cla ete e 96
OSORIOBR GS Cie ee aula ere ye ase ac eae Sen 311
] PDF UURIU a] Aan pray RENT ntetcer sem ok Le INST ae ale ere rete ned RO 330
| ES OCHO) aise De Sarna is ae rae aed Baca a eer (143)
JEN TIO) Os) hor ena aa LOO VD me eu PEE Moa 199
RIEKING TONGS BS: ciate cee ath ube eiaasieee ela a 229
JPAGLISTINIGARON IML, Choco coeeannadcedsaccnscovuce 229
IROORINGAN Se ele Ava ee eames te pert are veers evar 5
INOBINSO Nags tales Cease ane nea ene 26
ROTHER B: Bie Scars Mieniea aac hee ates (143), (332)
ISHIIMIR. Ke RES SIGS ioe tripe se eget Sista oaet nareas 10, 258, 274
IS MOTIDET a GROG ais oe a Oe el -mn RC EL ppe Nagra ee 37
S MINISEIERIRGOD oe toh, rere oe eee mer erate repent ee Ace 2,
SMITE abl suetonttc penny eae aa ie SET Ae ae ee ine Scare el 69
STACKHOUSEMC A Wis rarest ean res ego ites ee Aevent aes 145
SIRASEK ti Ge Reais a elenyay Ye aiden Seu nnu mn myteN circ cum ee 288
SRIRIEING SiR aaretye eee Ln sien Syn anaiie co Lrer ene 1a 229
AHONMPSON a Bina a ees, este Wien ae irae 188
ATISCOWM IASON Men Bs sve, ga, Seto a peemae lore bouts oeeea neuer amee 136
WIDINTYNIPNGTEIN, Ss A Ws coctonscocsauosucosue 305
VOTEDZ OWI To senate cuehoke ante wa gamete ta dececa 18
VVEANRIE: NA (as noes ennara ihe Be depot err Maerua At, 170
DV VSESSoie ole] a El oar erras secant beurre mn crane SUN esc dmc ae 199
VION OWAN Nik eee re entender tie pert ns Sinuta ke 214
Page numbers for book reviews are indicated by parentheses.
GW, pie ISSN 0042-3211
SYSNTION 4O NOISIAIC
THE, = wasvesi toticcs
% (IV H WITHA
VELIGER
A Quarterly published by
CALIFORNIA MALACOZOOLOGICAL SOCIETY, INC.
Berkeley, California
R. Stohler, Founding Editor
Volume 26 July 1, 1983 Number 1
CONTENTS
Our thanks to Rudolf Stohler
Pap Ie OVNI Mee weep ae nee OSI AMM ta ice ie aout fel Bt adele a als 2
New molluscan species (Gastropoda: Neogastropoda) from the tropical eastern
Pacific
RO Napisy e OORINVAING eyes tet cae ore Yap cf wean toy al hen es, sy aa ev nie aha IS Imei euege Ye olle 5
The biology of the northeastern Pacific Turridae. III. The habitat and diet of
Kurtziella plumbea (Hinds, 1843)
[Re Lia, STEMI TSC FG tha louse seat teades Aas remain at te ADs RRO Pete na ok Raat e non 10
Flow through and around the abalone Haliotis hamtschatkana
SAINI EMV OIMGZOW paar les icie re yh he aoee aired ese ay ee cis SUTIN, A UR ee at Be 18
Shell strength in Corbicula sp. (Bivalvia: Corbiculidae) from the Potomac River,
Maryland
WiICTORE SIKENNEDYSAND EJAY. Ac IBISUNDON) 2 qe) fst cele) ah neater 22
Relationship between beak morphometrics and live wet weight of the giant
Pacific octopus, Octopus dofleini martini (Wilker)
SHAWN M. C. ROBINSON AND E. BRIAN HARTWICK ................... 26
Studies on the reproductive biology of some prosobranchs from the coast of
Pakistan bordering the northern Arabian Sea. II. Egg capsules and larvae
of four species of Thais
SOEATION DS AIRIKCASInIe ANID) BV MUHA MIN OTIS NEUE) es) oe SARE ee eee 30
CONTENTS — Continued
The Veliger (ISSN 0042-3211) is published quarterly on the first day of July, October,
January and April for $18.75 for existing members (plus mailing charges) and $37.50
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THE VELIGER
Scope of the journal
The Veliger is open to original papers pertaining to any problem concerned with mol-
lusks.
This is meant to make facilities available for publication of original articles from a
wide field of endeavor. Papers dealing with anatomical, cytological, distributional, eco-
logical, histological, morphological, physiological, taxonomic, etc., aspects of marine,
freshwater, or terrestrial mollusks from any region will be considered. Short articles
containing descriptions of new species or lesser taxa will be given preferential treatment
in the speed of publication provided that arrangements have been made by the author
for depositing the holotype with a recognized public Museum. Museum numbers of the
type specimen must be included in the manuscript. Type localities must be defined as
accurately as possible, with geographical longitudes and latitudes added.
Very short papers, generally not exceeding 500 words, will be published in a column
entitled “NOTES, INFORMATION & NEWS”; in this column will also appear notices
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general.
Editor-in-Chief
David W. Phillips, 2410 Oakenshield Road, Davis, CA 95616, USA
Editorial Board
Donald P. Abbott, Emeritus, Hopkins Marine Station of Stanford University
Hans Bertsch, Universidad Autonoma de Baja California
James T. Carlton, Williams College—Mystic Seaport
J. Wyatt Durham, University of California, Berkeley
Cadet Hand, University of California, Berkeley
Carole S. Hickman, University of California, Berkeley
A. Myra Keen, Emerita, Stanford University
Frank A. Pitelka, University of California, Berkeley
Peter U. Rodda, California Academy of Sciences, San Francisco
Clyde F. E. Roper, National Museum of Natural History, Washington
Judith Terry Smith, Stanford University
Ralph I. Smith, University of California, Berkeley
Wayne P. Sousa, University of California, Berkeley
T. E. Thompson, University of Bristol, England
Alex Tompa, University of Michigan, Ann Arbor
Membership and Subscription
Membership in the California Malacozoological Society is open to persons (no institu-
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TO OUR READERS
The previous issue, Volume 25, Number 4, marked the completion of 25 years of growth and success of The Veliger,
success due in great measure to the efforts of one man, Rudolf Stohler. The climb is by no means over. With Volume
26, Number 1, we begin again, advancing by standing on the shoulders of our predecessors.
Some changes in format and style will be apparent to readers of the current issue. Our journal is now being produced
by Allen Press, a quality commercial printing house specializing in scholarly journals and books. And there is a new
Editor. Prospective authors may wish to consult the revised “Instructions to Authors” printed on the inside back cover.
There are some changes.
Despite these changes, our purpose remains the same. The California Malacozoological Society, through its journal
The Veliger, remains committed to disseminating new information in the field of malacology and conchology as widely
as possible at the lowest cost possible. We likewise reaffirm our continuing commitment to meeting ever higher standards
for the publication of scientific information.
There is no reason why The Veliger should not continue to grow for another 25 years. Our Society is vigorous and
healthy. However, ominously escalating costs of publication have already threatened many a once healthy society. The
simple truth is that we will need increased levels of income to balance our increased production costs. Readers can help
ensure the continued publication of The Veliger by joining the Society (or by renewing their membership) and by
encouraging their local and University libraries to subscribe. Donations are, of course, another extremely important
means of ensuring the success of our Society (contributions to CMS are tax deductible).
A new beginning is a time to reaffirm our purpose, to acknowledge the many splendid contributions that have brought
us this far, and to seek ways to improve. The new Editor asks you to support the Society and invites the comments of
readers, members, and prospective authors. He looks forward to serving you.
D. W. Phillips, Editor
Photograph by Leroy Poorman
RUDOLF STOHLER
OUR THANKS TO RUDOLF STOHLER
With the completion of Volume 25 of The Veliger, Dr. Stohler has retired as Editor—stepping aside for some well-
earned rest while still able to help us with his counsel and to inspire us with his unabated interest and enthusiasm. It
is a good time to look back over the history of The Veliger, and to reflect gratefully how much we owe to the efforts of
one devoted individual.
To many who have read and contributed to The Veliger, Rudolf Stohler may be simply an exacting Editor, a stickler
for accuracy and good order in writing; to those of us who from time to time have transgressed, he is one who can
communicate in pithy language; to those of us who have appealed for help, he has been ready with advice and assistance.
But Rudolf has done much more than found and edit The Veliger, and we should fill in the picture of his pre-Veliger
years, for information on which we are indebted to Professor Emeritus Richard Eakin, long-time Chairman of the
Department of Zoology at the University of California, Berkeley.
Rudolf Stohler earned his Ph.D. at the University of Basel in his native Switzerland, and in the period of 1926-1932
published a series of papers on the chromosomes of European toads and their ovaries and Bidder’s organs. He came to
California in 1928 as a Rockefeller Fellow to work with Dr. K. F. Meyer at the Hooper Foundation on the University
of California’s San Francisco campus. The first day, as he arrived at the laboratory early, as was and is his habit, he
picked up a large beetle that aroused his zoological curiosity. A young lady coming to work offered to obtain a bottle
for the specimen. The Fellow was impressed with her kindness and friendliness and decided, then and there, that he
wanted her for his wife. A year later Genevieve and Rudolf were married.
Dr. Stohler had expected to continue his study of sex determination and differentiation in amphibians, but Professor
Meyer had other plans for him, namely, that he work as an assistant on paralytic shellfish poisoning. At first it appeared
that diatoms, found in abundance by Stohler in the guts of mussels and clams, might be the source of the lethal poison.
Without more evidence Professor Meyer immediately published a paper, as sole author, to that effect. Later, Dr. Stohler
disproved that hypothesis. The source of the toxin was found to be Gonyaulax or other red tide flagellates that are eaten
by the bivalves.
After the.completion of the fellowship, the Stohlers emigrated to Switzerland, but as the climate was unsuitable for
the young bride the couple returned to Berkeley in 1932. Dr. Stohler was appointed a Research Associate (an honorary
title but without salary) by Professor C. A. Kofoid, then Chairman of the Department of Zoology, University of
California, Berkeley. Again Dr. Stohler was not free to pursue his own research because he was assigned to projects of
Kofoid’s. To earn a living Stohler organized classes in German. Among his students were Alden Miller, later a Director
of the Museum of Vertebrate Zoology, and Richard Eakin, later a Chairman of Zoology. In 1941 he was appointed to
the position of Specimen Preparator and Collector for the Department of Zoology. In these capacities he ranged the
California coast collecting for classes and for research, and developing a wide circle of friends and scientific colleagues.
Later, under the Chairmanship of Richard Eakin, Dr. Stohler was relieved of some of his service responsibilities by
appointment as a Research Zoologist (the research equivalent of a professorship) and was given an assistant and time
to devote to his malacological interests.
Dr. Stohler has also had a career of teaching. In 1934 he gave the departmental courses in cytology and assisted
Professor Kofoid in courses in protozoology and parasitology while Professor Harold Kirby was on sabbatical leave.
For many years he gave courses in the University of California Extension Division in Oakland, San Francisco, and
Berkeley. And he has generously advised graduate students and faculty on procurement of research material, on
nomenclatural and taxonomic problems, and on scientific writing.
In the early 1950’s Rudolf Stohler and several colleagues of like interests founded the Northern California Malaco-
zoological Club, the rather imposing name reflecting that the group was broadly interested in molluscan biology and
not merely in “‘shell-collecting.” On June 27, 1958, appeared a mimeographed Club newsletter, ““The Veliger,” suitably
named for an infant mollusc.
The new publication grew rapidly and by its fourth year contained 220 pages and had appeared in printed format—
made possible because Stohler had, out of his own pocket, acquired and set up in his basement an old linotype machine.
Over twenty years later, on this machine, now supplied with a dozen different type-faces, Stohler still regularly set type
for The Veliger, which since 1967 has run to over 400 pages annually.
After many years’ investment of Stohler’s skill and labor, not to mention over $7,000 of his own money, The Veliger
had clearly outgrown the needs of the Club and was incorporated by a small support group, the California Malaco-
zoological Society, as a non-profit corporation. Stohler, with only a part-time business assistant and the help of various
Photograph by Jane Scherr; courtesy of “California Monthly.”
individuals (notably Mrs. Jean Cate), carried on all the essential functions of editing, printing, and distributing the
journal, whose circulation is now over 800.
The corporation undertook to repay Stohler his $7,000 investment. But, in setting up the corporation, Stohler had
instituted an endowment fund, the capital of which cannot be touched, but the income from which can be used to help
support publication, for example, of papers with expensive illustrations that cost more than an author can afford. As
fast as the corporation paid back installments on the debt, Stohler put the money into the Endowment Fund, to aid the
publication (contributions to this fund have come from many friends and are, of course, still enthusiastically welcomed).
The success of The Veliger, which has never received a penny of foundation support, is a remarkable example, in
this day of heavily-funded, group-supported ventures, of what one person with skill, energy, and devotion can accomplish.
The first 25 volumes of The Veliger form a fitting and living monument, and it is our hope and intention that Rudolf
will see it flourish for many years to come.
To characterize Rudolf Stohler as a person is not easy. Even more solid than The Veliger, Rudolf radiates energy
and enthusiasm. Generally at the Zoology Department well before anyone else, Rudolf moves with a brisk, perhaps
bouncy, style. Extremely helpful to those needing and seeking his help, and sympathetic to personal needs of students,
Rudolf is yet one who does not suffer fools gladly. Above all, he detests sloppiness in anything, physical or mental. His
choicest comments have been reserved for his favorite béte noir, the U.S. Postal Service, but others have not escaped.
Yet all who have known Rudolf know that behind the sometimes pungent manner there lies a deep decency, integrity,
kindness, and high personal standards. Rudolf has not lightly retired as Editor of The Veliger, and doubtless feels like
many a parent watching his child venture out into the world. His principal concern is that The Veliger maintain high
standards. To this aim the Executive Committee of the California Malacozoological Society and the new Editor are
committed.
A final word needs to be said. In all his work for over 50 years Rudolf has had the support of his devoted wife,
Genevieve, who has shared heavily in the labor and frustrations of producing The Veliger. Although inconspicuous in
the background, she has nevertheless earned our deepest gratitude.
R. I. Smith
The Veliger 26(1):5-9 (July 1, 1983)
THE VELIGER
© CMS, Inc., 1983
New Molluscan Species (Gastropoda: Neogastropoda)
from the Tropical Eastern Pacific
LEROY H. POORMAN
15300 Magnolia Street, Space 55, Westminster, California 92683
Abstract.
Three new species are described: Murexiella venustula Poorman, spec. nov., off the south-
ern coast of Isla Santa Cruz, Galapagos Islands, Ecuador, and probably the Gulf of California; Daph-
nella levicallis Poorman, spec. nov., off Estero San Carlos, Sonora, Mexico; Anachis (Parvanachis)
mullineri Poorman, spec. noy., in Bahia de Santiago, Colima, Mexico.
TWENTY-NINE YEARS of observing and collecting mollusks
along the west coasts of the Americas has resulted in the
recognition of a number of new species, eight of which
have already been published. Three additional species are
described herein.
Murexiella Clench & Pérez Farfante, 1945
Type species: Murex hidalgoi Crosse, 1869, by original
designation.
The small, stoutly fusiform shell has four or more var-
ices with foliated spines connected by a laminated web-
bing. The siphonal canal is moderately broad and extend-
ed. The operculum is muricoid, with a sub-apical nucleus.
Murexiella venustula Poorman, spec. nov.
(Figures 1, 2, 5)
Description: The shell is small and solid, consisting of
five whorls and a turbinate protoconch of three turns.
Axial sculpture is of seven strong, broad varices per whorl
with narrow interspaces. Each varix crosses the shoulder
area to the preceding whorl as a thin lamella but is not
joined to it. The first several varices of the teleoconch cross
the lower half of the last turn of the protoconch and are
attached to it. Spiral sculpture on the body whorl is of five
broadly flattened, strong cords that are made up of five
scabrous threads. There are two cords on each whorl of
the spire. All interspaces are narrow, wider at the bottom.
At the base of the aperture is one minor cord and there
are two strong, flattened cords on the canal. Anterior cords
are hollow at their terminations and scarcely reflected as
short, stout spines at the crests of the varices. The degree
of reflection increases posteriorly along the varix. The
cord at the shoulder is the heaviest and terminates as a
large, reflected spine that is twisted toward the apex. There
is a major, reflected, open spine at the center of the lamella
on the shoulder and a much smaller one near the suture.
Areas on the shoulder between the lamellae are flat and
show only traces of the two cords causing the spines. The
aperture is oval with a nearly complete peristome except
along the parietal wall. A shallow, anal sulcus is apparent.
Strong crenulations are along the erect outer lip. The spines
behind the lip are roundly recurved and are joined for
about half their lengths by intricate lamination. The an-
terior canal is broad and moderately long, nearly straight,
narrowly open to the right, and with the end distally re-
curved. The top and left side of the canal each show four
strong, longitudinal threads. Shell color is pinkish beige,
with brown on the third spiral cord at the crests of the
varices.
Type locality: Off the southern coast of Isla Santa Cruz,
Galapagos Islands, Ecuador; 0°47’S Latitude, 90°21/W
Longitude; four specimens dredged in 150-200 m.
Holotype: San Diego Natural History Museum,
SDNHM 810610.
Dimensions of the holotype: Height 19.6 mm, maxi-
mum diameter 11.4 mm.
Paratypes: Iwo paratypes are in the Carl and Laura Shy
Collection, Seal Beach, California; one paratype is in the
Rose Burch Collection, Seal Beach, California.
One additional specimen was brought in by a fishing
boat to Guaymas, Sonora, Mexico, in 1968, probably ex-
tending the range to the Gulf of California.
The specific name is taken from the Latin adjective
meaning “pretty” or “charming little.”
5 INO: 1
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L. H. Poorman, 1983
Page 7
Discussion: This new species is closest to Murexiella mil-
dredae Poorman, 1980, in general appearance and in the
low, broad, spiral cords overhanging the narrow inter-
spaces (POORMAN, 1980b). It differs in having two, not
three, spiral cords on each whorl of the spire, in having
numerous and broadly rounded varices, in coloring, and
in other sculptural details.
Murexiella venustula, spec. nov., also has a superficial
resemblance to Murexiella laurae Vokes, 1970. However,
the latter species has a different spine structure and has
four varices per whorl (only three on some specimens) on
the adult shell (POORMAN, 1980a). Also, the general col-
oring of the two species is completely different.
Hollow spines formed when the leading edges com-
pletely circle to touch are not unusual in Murexiella. All
three of the above species are of this type. Comparison
was made with a specimen of Murexiella mactanensis
Emerson & D’Attilio, 1979, from Bohol Strait, Philippine
Islands. Although the shells differ in general appearance,
the basic spine structure is similar.
Daphnella Hinds, 1844
Type species: Pleurotoma lymneiformis Kiener, 1839-1840.
The shell is cylindro-ovate, slowly contracted to a short,
open, truncated, anterior canal. The body whorl is usually
more than one-half the shell height. The protoconch is
reticulated and of three to four turns. The sinus is sutural,
reversed L-shaped. Spiral sculpture is of fine threads over-
riding numerous fine, axial ribs. There is no operculum.
The shell is irregularly maculated with brown.
Daphnella levicallis Poorman, spec. nov.
(Figures 3, 6)
Description: The shell is larger and more inflated than
most species in the genus. The protoconch (eroded on the
holotype) is of four turns, narrowly turbinate and diago-
nally reticulated by fine threads, with small beads at the
intersections. The first turn of the protoconch is minute
and has small beads (at 250X) arranged in spiral rows
and diagonal lines which, by the second turn, become di-
agonal threads. The last half turn of the protoconch de-
velops a slight, peripheral angulation with the reticula-
tions above the angulation sagging into a band and
becoming the trace of the anal sulcus on the teleoconch.
The angulation becomes a cord that develops into two
l 0.5 mm
Figure 5
Protoconch of Murexiella venustula Poorman, spec. nov. X 80.
threads. These develop into the spiral cords on the teleo-
conch. The protoconch terminates abruptly in a sinuosity
advancing anteriorly. The teleoconch is of six rounded
whorls constricted at the suture. Spiral sculpture is of
strong threads throughout, 2 on the first turn and 25 on
the body whorl. The trace of the anal sulcus is wide and
flat, unornamented except for obscure fine threads. Axial
sculpture is of numerous low rounded ribs, 10 on the first
turn and 25 on the body whorl, extending to the anterior
canal. Ribs are crossed by spiral threads in prominent
nodes, strongest at the shoulder. The aperture is oval, with
a deep J-shaped anal sulcus at the suture. The pillar is
nearly straight anteriorly and has light callus. The outer
lip is flaring but not produced forward, with a pronounced
sinuosity at the lower part. A short, truncated, open, an-
terior canal is differentiated from the aperture by an an-
gulation in the lip. The outer lip is reinforced by a low
ridge of callus just inside, thickest at the anal sinus and
at the anterior part of the aperture. Shell color is pale
brown maculated with red-brown except for an unmac-
ulated band below the periphery. The third spiral cord
below the shoulder is white on early whorls.
Type locality: Five km south of Tetas de Cabra, Estero
San Carlos, Sonora, Mexico; 27°54’N Latitude, 111°05’W
Longitude; 16 specimens dredged in 80-100 m on broken
shell, small rocks, and silt bottom.
Explanation of Figures 1 to 4
Figure 1. Holotype of Murexiella venustula Poorman, spec. nov.
x 5.6.
Figure 2. Holotype of Murexiella venustula Poorman, spec. noy.
x 5.6.
Figure 3. Holotype of Daphnella levicallis Poorman, spec. nov.
xX 6.0.
Figure 4. Holotype of Anachis (Parvanachis) mullineri Poor-
man, spec. nov. X 22.
Page 8
0.5 mm l
Figure 6
Protoconch of Daphnella levicallis Poorman, spec. nov. X 90.
Holotype: San Diego Natural History Museum,
SDNHM 810611.
Dimensions of the holotype: Height 17.3 mm (apex
eroded), maximum diameter 7.2 mm.
Paratypes: Nine paratypes are in the Forrest and Leroy
Poorman Collection; two paratypes are in the Carl and
Laura Shy Collection, Seal Beach, California; four para-
types are in the Paul and Carol Skoglund Collection,
Phoenix, Arizona; one paratype will be placed at the
Academy of Natural Sciences of Philadelphia.
One additional specimen was dredged by Paul and Car-
ol Skoglund in 100 m off Isla Danzante, Gulf of Califor-
nia.
The specific name is a Latin noun, masculine gender,
and refers to the subsutural trace of the anal sulcus as a
“smooth mountain path” much like the path up the Tow-
er of Babel.
Discussion: All of the recognized west American Daph-
nella and the new species described here are very similar,
differing only in size and details of ornamentation. The
mechanism for developing the trace of the anal sulcus is
observable on all. This subsutural band is also observable
on the teleoconchs but is obscured except on Daphnella
retusa McLean & Poorman, 1971, and the new species.
Thickening of the outer lip occurs both internally and
externally on the adults of all the species.
Both Daphnella retusa and Daphnella levicallis, spec.
nov., occur in significant numbers off Estero San Carlos
but differ in their bathymetric ranges and habitats. Daph-
nella retusa is found in 30 m on gravel bottoms; whereas
D. levicallis is found in 100 m on shell and silt bottoms.
Daphnella levicallis is larger, heavier, and of a darker
color; the axial ribs are not obsolete on the body whorl,
as they are on D. retusa, but extend nearly to the anterior
canal. The ribs are crossed by strong spiral cords in prom-
inent nodes not occurring on D. retusa. The trace of the
anal sulcus is broader and flatter on the new species, with
The Vielicers Volk ZG Nom
Figure 7
Protoconch of Anachis (Parvanachis) mullinert Poorman, spec.
nov. X 30.
the axial ribs projecting slightly at their terminations to
give a beaded effect to the shoulder.
Anachis (Parvanachis) Radwin, 1968
Type species: Buccinum obesum C. B. Adams, 1845.
The shell is small and obese, with a moderately high
spire and flat-sided whorls with incised sutures. Body
whorl and spire are of equal length. The apertural lip is
thickened and denticulated. Sculpture is of prominent ax-
ial ribs crossed by spiral cords.
Anachis (Parvanachis) mullineri Poorman, spec. nov.
(Figures 4, 7)
Description: The shell is small and stout, consisting of a
turbinate protoconch of four smooth turns and a teleo-
conch of three and one-fourth whorls, terminating in a
large, rounded, lip varix that decreases in size anteriorly.
Transition from protoconch to teleoconch begins with
weak, slanted ribs advancing anteriorly. The transition
takes about one-half whorl when the ribs become longi-
tudinal, rounded, and with equal interspaces. There are
about 20 ribs on each whorl. The ribs are abruptly con-
stricted just above the indented suture to leave widened
areas in the interspaces. The ribs are rounded, protrude
slightly above the shoulder, and are obsolete on the base.
A spiral groove just below the indented suture cuts the
ribs to produce a row of squarish beads. Below this is a
region with no spiral sculpture. The middle half of the
body whorl shows nine strong spiral grooves in the inter-
spaces of the ribs. On the base, the spiral grooves override
the diminishing ribs producing strong, flat-topped spiral
cords. The entire surface of the teleoconch is covered with
minute, spiral striae. The narrow aperture is somewhat
trapezoidal. The outer lip is sharp, erect, and slightly
crenulated by the spiral cords overriding the lip varix.
Within the outer lip are six denticles. Columellar callus
L. H. Poorman, 1983
is produced into a lamella with a chink behind, both of
which extend to the end of the canal (chipped on the
holotype). Within the aperture, along the pillar, is a lon-
gitudinal ridge of callus with six denticles. The anal sul-
cus is semicircular in cross section and slightly constricted
by parietal callus. The sulcus penetrates the outer lip and
varix at an angle of 60° with the axis and curves to ter-
minate at an angle of 90°. The short, anterior canal is at
an angle of 30° left of the shell axis, scarcely differentiated
from the aperture, and broadly open to the right. The
shell is light horn color with a band of darker brown above
the periphery and a second indefinite band on the base.
Type locality: Bahia de Santiago, Colima, Mexico;
19°02’N Latitude, 104°28’W Longitude; five specimens
dredged in 20 m on sand and gravel bottom.
Holotype: San Diego Natural History Museum,
SDNHM 81612.
Dimensions of the holotype: Height 5.0 mm, maximum
diameter 2.8 mm.
Paratypes: Four paratypes are in the Forrest and Leroy
Poorman Collection.
Additional specimens in the Paul and Carol Skoglund
Collection, Phoenix, Arizona, are from: Cuastecomate,
Jalisco, dredged in 25-33 m; La Cruz de Juanacaxtle,
Bahia de las Banderas, Nayarit, dredged in 20 m; Playa
Novellero, Nayarit, diving in 8-12 m.
The specific name is chosen in recognition of David K.
Mulliner, San Diego, California, a good friend known to
all for his generous contributions of time and talent to the
field of malacology.
Page 9
Discussion: The massive lip varix and the unusual anal
sulcus curving across it, together with the erect lamella
along the pillar, are distinctive and make further compar-
ison with other existing taxa unnecessary.
ACKNOWLEDGMENTS
I wish to recognize with thanks the contributions of An-
thony D’Attilio, San Diego Natural History Museum,
who made the protoconch drawings, and David Mulliner
for technical assistance in preparing the illustrations.
LITERATURE CITED
CLENCH, W. J. & I. PEREZ FARFANTE. 1945. The genus Mu-
rex in the western Atlantic. Johnsonia 1(17):1-56.
EMERSON, W. K. & A. D’ATTILIO. 1979. Six new living species
of muricacean gastropods. Nautilus 93(1):1-10.
HInps, R. B. 1844{-1845]. The zoology of the voyage of H.M.S.
Sulphur ... Mollusca, pt. 2, pp. 25-48 (published October
1844) London.
McLean, J. H. & L. H. PooRMAN. 1971. New species of
tropical eastern Pacific Turridae. Veliger 14(1):89-113.
PoorMAN, L. H. 1980a. Reinstatement of two species of Mu-
rexiella (Gastropoda: Muricidae) from the tropical eastern
Pacific. Veliger 22(3):273-276.
PooRMAN, L. H. 1980b. Two new molluscan species (Gas-
tropoda: Muricidae) from the tropical eastern Pacific. Ve-
liger 22(4):361-363.
RapDwIn, G. E. 1968. New taxa of western Atlantic Colum-
bellidae. Proc. Biol. Soc. Wash. 81:143-150.
VoKEs, E. H. 1970. The west American species of Murexziella
(Gastropoda: Muricidae), including two new species. Veli-
ger 12(3):325-329.
The Veliger 26(1):10-17 (July 1, 1983)
THE VELIGER
© CMS, Inc., 1983
The Biology of the Northeastern Pacific Turridae.
III. ‘The Habitat and Diet of
Kurtziella plumbea (Hinds, 1843)
by
R. L. SHIMEK'
Friday Harbor Laboratories, Friday Harbor, Washington 98250
Abstract.
The habitat, diet, and some reproductive and mortality factors were determined for Kurt-
ziella plumbea, a shallow-water turrid gastropod from the Puget Sound region. In a shallow subtidal
area with four depth-related habitats, it was found more often in upper habitats, although all of the
habitats available were sandy and had similar sedimentary characteristics. In a deeper area, it was
found primarily in areas of silty mud. Kurtziella plumbea is a predator of polychaetes. At the shallow
site, it specialized on the oweniid Owenia fusiformis and spionids. In the deeper area, it was more
generalized, but the cirratulid Tharyx multifilis was the most abundant prey item.
Egg capsule deposition occurred in the spring. There were no nurse eggs, and the time until veligers
left the capsule was about 18-20 days. Settlement and metamorphosis were not observed. Growth rates
of 1 to 2 mm/yr for median-sized individuals, and 3 to 4 mm/yr for small individuals were indicated.
Potential predators may include crabs and fish, but mortality factors were not conclusively deter-
mined.
INTROIDUCTION
THE MOST WIDELY distributed turrid gastropod in the
shallow northeastern Pacific is Kurtzzella plumbea (Figure
1), which is found from Mazatlan (MCLEAN in KEEN,
1971) to southcentral Alaska (Shimek, unpublished data).
I examined two populations of Kurtziella plumbea (here-
after as Kurtzzella) to determine habitat, dietary require-
ments, and aspects of predatory and reproductive behav-
ior. I attempted to determine some of the reasons why this
particular snail is so widespread. Two mutually contra-
dictory statements about this species were examined. (1)
The species is generalized in both its use of habitats and
prey, and thus it can be found in many habitats. In effect,
it would be a successful “Jack-of-all-trades.” (2) The
species is specialized in habitat and/or diet, but the array
of suitable habitats is widespread, thus permitting the snail
to be widespread. Several major questions were addressed.
(1) What is the relationship of diet to the potential dietary
resources present? (2) Are these animals dietary or habitat
' Current mailing address: P.O. Box 6683, Bellevue, Wash-
ington 98008.
specialists or generalists? (3) What is the effect of these
predators upon their prey populations? (4) Are there any
particular traits that limit their choices of habitats or prey?
MATERIALS anp METHODS
Study Sites
All sites were subtidal, since Kurtziella is rarely inter-
tidal in this region. Two major study sites were chosen:
Windy Point in Dyes Inlet in lower Puget Sound and off
the University of Washington Friday Harbor Laborato-
ries dock on San Juan Island (Figure 2). Additional spec-
imens were collected from many other localities, particu-
larly in the San Juan Islands (SHIMEK, 1977); however,
at these latter sites I collected only distributional data;
quantitative data were seldom obtainable. Distributional
information was gathered by dredge or bottom tow. All
quantitative field work was done using SCUBA.
The Windy Point area, WP (47°37’25’N, 122°
40’30”W), ranges from —1.5 m to —9.0 m below MLLW.
It is a topographically homogeneous, sandy subtidal re-
gion unbounded laterally and divisible into four visually
distinctive habitats: upper bench, upper slope, lower slope,
R. L. Shimek, 1983
Page 11
Figure 1
A. Kurtziella plumbea (Hinds, 1843). Scale in millimeters. B. Radular teeth of Kurtziella plumbea. Scale bar = 10
um. These are stabbing toxoglossan teeth used individually to pierce the prey and to introduce venom.
and lower bench, based upon the degree of slope, depth,
and algal cover (SHIMEK, 1982). Kurtziella is found there
with two other turrids, Ophiodermella inermis (Hinds,
1843) and Oenopota levidensis (Carpenter, 1864).
The Friday Harbor Laboratories site, FHL (48°
32/38”N, 123°00’50”W), is topographically diverse, con-
taining five visually distinctive habitats: wood chips, rock,
shell fragments, and shallow and deep areas of silty mud.
The site is located from —10 m to —25 m below MLLW.
No discontinuities limit the site except at the upper edge
where the boundary is established by the lower edge of
an eelgrass, Zostera marina L., 1753, bed. No turrids were
found in either the eelgrass or wood-chip areas in prelim-
inary observations, consequently no quantitative sampling
was done in either habitat. The remaining habitats were
sampled quantitatively.
Page 12
mrAAaAbPMo
Figure 2
The Puget Sound region of Washington state showing the study
sites.
Habitat Analyses
At the major sites, the physical and biological properties
of the habitats were examined in detail. Sediment particle-
size distributions were quantitatively determined and the
remainder of the sample was washed through a 0.5-mm
sieve. The animals were removed and sorted by taxon.
Gastropods and polychaetes were identified to species
whenever possible. Other taxa were identified to class and
counted, but not detailed further (see SHIMEK, 1982, for
a more complete description of sampling methods).
Sediment parameters were tabulated and statistically
compared between and within the areas. Seasonal vari-
ability of the sediment particle distributions was insignifi-
cant, thus no seasonal comparisons were made (SHIMEK,
1982).
Polychaete assemblage abundances for each habitat were
determined by the quantitative, infaunal sampling, and
The Veliger, Vol. 26, No. 1
statistical comparisons were made between and within
habitats on a seasonal basis (SHIMEK, 1982).
Turrid Distribution, Collection, and Processing
Periodic transect studies from November, 1973, until
December, 1975, were used to determine turrid distribu-
tion, seasonal or other distributional changes, and to pro-
vide a reference for the quantitative infaunal samples. ‘The
significance of Kurtziella distributions compared to ran-
dom habitat utilizations were calculated using log-likeli-
hood ratios (G-tests) (SOKAL & ROHLF, 1969).
A hand-held, semiquantitative dredge was used at FHL
to determine the relative fraction of the turrid populations
buried in the sediment. Simultaneous, parallel, surface-
transect surveys were conducted to compare the number
of snails buried and on the surface.
Kurtziella collected from FHL and WP were individ-
ually washed in sea water, isolated for up to a week, and
feces were collected. The snail was then measured to the
nearest 0.1 mm, and marked (SHIMEK, 1982). After mark-
ing, the animal was returned to fresh sea water at ambient
sea-water temperature and observed to assure no notice-
able effects of measuring and marking. The animal was
then transferred to a “holding” aquarium and maintained
in an artificial habitat similar to the normal one. All ap-
parently healthy animals were returned to their habitat,
albeit seldom to the point of capture, within two weeks.
Measuring and marking mortality was about five percent.
Following marking and measuring, any particulate ma-
terial remaining in the collecting jar was placed on a slide,
dried, mounted in polyvinyl lactophenol (A. Kohn, per-
sonal communication), and examined microscopically.
Identification of all fecal material was attempted. Feces
consisted of mucus, radular teeth of the same animal,
diatom frustules, and polychaete remains. Preliminary gut
analysis by dissection indicated polychaetes swallowed
whole to be the only prey. Thus only polychaete remains
consisting of setae, Jaws, and occasional cuticular strips
were accepted as indicators of feeding. These remains were
identified by comparison with descriptions, drawings, and
setal preparations of known animals, identified with stan-
dard references (SHIMEK, 1982). Dietary heterogeneity was
measured using H’ (KOHN & NyYBAKKEN, 1975). Turrids
collected from other localities were preserved and their
habitats noted, if the collecting was done with SCUBA,
but no dietary analysis was attempted.
Size-frequency histograms were constructed for both
populations. These were normalized to percent collected
to facilitate comparison between populations because of
varying sample sizes. For the purpose of determining
growth rate, collections were considered quarterly: No-
vember through January as Winter; February through
April as Spring; May through July as Summer; and Au-
gust through October as Autumn. Generally these samples
were too small and/or variable for quantitative determi-
nations of recruitment cohorts (BLISS, 1967); however, I
R. L. Shimek, 1983
Page 13
attempted to use seasonal shifts in histogram peaks to
estimate growth rates.
Laboratory Experiments
A substrate-choice chamber was constructed, and filled
to a depth of 2 cm with sediments (SHIMEK, 1982). The
choices were sediments with a particle-size distribution
from 0.250 to 0.500 mm, and a distribution in excess of
2.00 mm. Both sides had all detectable biota removed.
Animals were placed in the chamber and one week later
they were collected and their positions noted. These data
were analyzed using cumulative binomial probabilities.
Egg capsules were collected from the jars in which the
turrids were stored. Capsular dimensions were measured,
the number of eggs per capsule was counted, and the egg
diameters were measured (SHIMEK, 1982). The capsules
were examined periodically. After hatching, the veligers
were fed a mixture of Isochrysis sp. and Dunaliella sp.
RESULTS
Habitat Descriptions
Windy Point: The four Windy Point habitats have been
described in detail elsewhere (SHIMEK, 1982). Briefly, these
habitats were sandy, with moderately well-sorted, uncon-
solidated sediments. They were similar to each other and
to the nearby sandy low intertidal areas. Algal cover in
the shallower (depth < —5 m) areas varied seasonally,
being very abundant in the late summer, and was mostly
ulvoid algae. In the deeper areas the algal cover consisted
of various red and brown algae and was less variable or
dense.
Friday Harbor Laboratories: The FHL habitats are also
described in SHIMEK (1982). Of the four major turrid
habitats, only the rock areas could not be sampled quan-
titatively for infauna and sediment. Of the three un-
consolidated-sediment areas, only the lower mud was
physically different, having a distinctly smaller median-
sediment-particle size.
Biology of Kurtziella at Windy Point
Kurtziella was associated with the turrids Ophiodermella
inermis and Oenopota levidensis at WP. All three were
distributed in patches, and because of this, the mobility of
these animals, asd the lack of physical boundaries to the
study area, no adequate estimates of population sizes could
be made. Capture and transect observational frequencies
did, however, give an estimate of relative population sizes.
I collected or observed 254 Ophiodermella inermis, 134
Kurtziella, and 108 O6enopota levidensis. Kurtziella and
Oenopota levidensis appeared to have roughly equivalent
populations. During quantitative surveys, the density of
Kurtziella, when found, varied from 0.01/m? to 0.16/m?.
No seasonal trends in abundances or habitats utilized were
seen, but Kurtziella was found more often in the shallower
Table 1
Windy Point Kurtziella plumbea habitat utilization.
Proportion
of turrids
Proportion Proportion observed —
of total of turrids proportion
Habitat area per area expected
Upper bench 0.25 0.34 +0.09
Upper slope 0.25 0.26 +0.01
Lower slope 0.25 0.17 —0.08
Lower bench 0.25 0.24 —0.01
Number observed 134
Significance (G-test) G = 9.40 P < 0.05
areas at WP (Table 1). The sediment-particle distribu-
tions were not significantly different among most of these
areas (SHIMEK, 1982). Depth was probably not a factor
as Kurtziella was found in the deeper areas at FHL (Ta-
ble 2).
There was a patchy distribution of the polychaete fauna
at WP, particularly regarding the turrid prey species Ow-
enia fusiformis delle Chiaje, 1844, which was dense only
in the upper bench areas, and Polydora socialis (Schmarda,
1861), which was more widely distributed than O. fuszfor-
mis (Table 3). There was no seasonal pattern of predation
at either site, consequently the prey-polychaete-abun-
dance data were pooled. The high sample variability re-
flected seasonal abundance patterns for the worms; see
Table 2
Friday Harbor Laboratories Kurtziella plumbea habitat
utilization.
Propor- Proportion
Propor- tion of of turrids
tion of _ turrids observed —
total per proportion
Habitat area area expected
A. All habitats
Upper mud 0.25 0.06 —0.18
Shell fragments 0.34 0.35 +0.01
Rock 0.05 0.06 +0.01
Lower mud 0.36 0.52 +0.16
Total number observed 48
Significance (G-test) P < 0.01
B. Lower habitats only
Shell fragments 0.45 0.38 —0.07
Rock 0.07 0.07 0.00
Lower mud 0.48 0.56 +0.08
Number observed 45
Significance (G-test) n.s.
Page 14
A. Area: Windy Point
Habitats:
Prey species
The Veliger, Vol. 26, No. 1
Table 3
Density of prey species (mean number/m? + 1 SD).
Upper bench Upper slope
Lower slope
Lower bench
Owenta fusiformis 713 + 413 IG se 37/5) ) ar DD 0
Polydora socialis 843 + 907 661 + 591 468 + 440 268 + 440
Spiophanes berkeleyorum Ole F 0 5 + 16 0
B. Area: Friday Harbor Laboratories
Habitats: Upper mud Shell fragments Lower mud
Prey species
Myrvochele oculata 6 ae iY) 0 0
Cirratulus cirratus Sil ae 56) 23) 22 Si 7X0) ae 37
Tharyx multifilis 136 + 125 YS 22 T7/ 1B) = (35)
Spiophanes bombyx
not sampled
SHIMEK (1977, 1982) for more complete listings of the
polychaetes.
Kurtziella was found to be widely, but unevenly, dis-
tributed in the Puget Sound region. I dredged and/or
surveyed by SCUBA 40 different sites and Kurtziella was
found in only six of them (SHIMEK, 1977). All six were
characterized as sandy or sandy-mud habitats.
Dietary Analysis
Dietary information obtained by fecal examination is
summarized in Table 4. Kurtziella at WP ate three species
of identified polychaetes. Densities of the most common
prey, Owenza fusiformis, fluctuated dramatically in all but
the upper-bench area, and this worm was absent from the
lower-bench area completely (Table 3).
Predation on Kurtziella at WP
In the WP-slope habitats predation by crabs upon the
snails may have been an important factor. Two predatory
Table 4
Results of fecal sample analysis of Kurtziella plumbea.
Area: WP FHL Total
Prey species
Myrtochele oculata 1 1
Owenia fusiformis 13 13
Polydora soctalis 1 1
Spiophanes berkeleyorum 2 2
S. bombyx 1 1
Cirratulus cirratus 1 1
Tharyx multifilis 3 3
Unidentified polychaetes 1 4 5
Number of snails examined 139 110 249
Percent feeding 22 9.1 10.8
H’ (identified prey only) 0.60 1.24 1.36
crabs were present, Cancer gracilis Dana, 1852, and C.
productus Randall, 1839, although specimens of the latter
were uncommon, probably because of too few suitable
refuges (SHIMEK, 1982). During the summer when the
crabs were common, Kurtziella became rare (Figure 3).
Consequently, no laboratory verification of the attractive-
ness of Kurtziella as a prey item was attempted. Cancer
productus will eat both Oenopota levidensis and the larger
Ophiodermella inermis in the same area, and Cancer gra-
culis may eat small snails of all types. As Kurtziella was
smaller than the other turrids at WP, it was a likely prey
item for both crabs.
Biology of Kurtziella at Friday
Harbor Laboratories
The turrid assemblage at FHL is diverse, in addition
to Kurtziella, nine other turrids in three other genera are
found there (SHIMEK, 1982, 1983). Habitat utilizations
were determined from transect surveys. As with the other
turrids at FHL, Kurtziella was less common in the upper-
mud area than would be expected if it was randomly
distributed (SHIMEK, 1982, 1983). If the upper-mud area
is considered to be a boundary area that is incompletely
utilized, and the data from this habitat are excluded, Kurt-
ziella was collected most frequently in the lower-mud hab-
itat (Table 2). When found, Kurtziella had measured
abundances from 0.01/m? to 0.05/m*.
The polychaete fauna at FHL was diverse and sparse.
The most abundant turrid prey, Tharyx multifilis (Moore,
1909), were present in most of the samples and habitats
(Table 3). The infaunal assemblages from all of these
habitats were similar in the summer, but in the winter
the upper- and lower-mud areas had many differences
(SHIMEK, 1982).
The substrate-preference experiments gave conclusive
results, even with the small number of individuals avail-
able at any one time for each test. Of the animals tested,
R. L. Shimek, 1983
Page 15
17 animals made choices; 13 chose the sediment with
smaller particle-size distribution (0.250 mm-—0.500 mm),
whereas only 4 chose the sediment with particles larger
than 2.00 mm. The two-tailed binomial probability of a
deviation this large or larger, given an equal probability
of choice, is 0.049.
The hand-held, semiquantitative dredge was used in-
frequently as it resulted in substantial habitat damage.
Data from these dredge samples indicated equivalent
numbers of Kurtziella buried and on the surface at the
times of the surveys. During the surface surveys, five
Kurtziella were found in 583 m?’. Simultaneous dredging
parallel to, but 2 m lateral to the surface-survey-transect
lines collected one Kurtziella in 116.6 m?® dredged to a
depth of 0.10 m.
Dietary Analysis
Relatively few animals were found eating (Table 4),
and no seasonal dietary trends were evident. At WP, Kurt-
ziella was most often feeding on Owenia fusiformis, al-
though spionids were also found in the diet. At FHL, no
such clear-cut pattern of specialization was evident, and
the snails had a more catholic diet consisting of cirratulids,
spionids and oweniids. In contrast to the prey distribution
at WP, the major prey taxon at FHL, the Cirratulidae,
was common in all habitats (Table 3).
Kurtziella Reproduction
Collection and confinement for fecal-sample examina-
tion acted as stimuli for egg-capsule deposition in some
turrids (SHIMEK, 1982, 1983). Eight individuals of Kurt-
ziella deposited egg capsules in captivity in March, April,
and May, 1975 (Table 5). Single females deposited from
one to three capsules. Capsules were smaller than the egg
capsules of either Oenopota or Ophiodermella, and con-
tained fewer, smaller eggs (SHIMEK, 1982, 1983). The egg
capsules were deposited on the inside of the collection jar
at the junction of the lateral and bottom surfaces. The
eggs in 10 capsules hatched after about 18-20 days. As
with Oenopota and Ophiodermella, there were no nurse
eggs, and the number of veligers leaving the capsules was
the same as the original number of eggs deposited. Four
capsules contained eggs that did not develop at all. Pre-
sumably the stimulus for oviposition was so strong that
unfertilized eggs were deposited in the capsules. These
capsules appeared normal in all other respects. No egg
capsules of Kurtziella were seen in the field.
Life Histories
Seasonal size-frequency distributions can be examined
for indications of growth rate, recruitment, and sizes of
individuals in the population. A comparison of the FHL
and WP populations yields some interesting observations.
The WP population was composed of distinctly smaller
individuals with virtually no animals exceeding 12 mm
S ce)
Oo Oo
S fe)
Ae)
(e)
ine)
Cancer observed
Kurtzie//a collected
SPR SUM AUT WIN
Season
Figure 3
Mean (+1 SD) number of Kurtziella plumbea (open bars) col-
lected and mean number of Cancer gracilis (black bars) observed
(per 25 m?) by season. All habitats and seasons were pooled.
Data are for Spring, 1974, through Autumn, 1975; therefore,
Kurtziella was collected in only one winter.
total length (Figure 4). On the other hand, the FHL pop-
ulation was composed of larger animals, with almost no
animals below 10 mm total length (Figure 5). Neither
population showed appreciable seasonal shifts in the size-
frequency histograms, although in both populations the
mean individual length increased from spring to winter,
and dropped again the following spring. The pattern of
changes in the mean sizes in both distributions was vir-
tually identical although consistently displaced by the
amount the two populations differed in mean length. Ex-
amination of the seasonal shifts for both populations in-
Table 5
Kurtziella plumbea reproductive information.
Mean capsule Mean egg
SISO NB) Number/ Diameter
Length Width capsule (um)
230 + 34 186 +22 180+ 43 137+8
Number examined 13 6 9
Number of capsules hatching: 10
Mean number of days in the capsule: 19.3 + 1.16 days
Maximum length of survival post hatching: 27 days
Page 16
The Veliger, Vol. 26, No. 1
WINTER 1974-75
N=19
SPRING 1974
N= 43
40
Ow
2 26
oO
v
Oo
oO
S
=
2 SPRING 1975 SUMMER 1975
: 404 N=4!
X&
(e}
aS QO
5 10 15 5 10 IS
Length (mm)
Figure 4
Windy Point seasonal size-frequency distributions. In seasons
not shown (Summer, Autumn, 1974) too few snails were ob-
served to make the data meaningful.
dicated a growth rate, for a 7-8 mm-long individual, of
about 1.5 mm/yr. No marked animals were recaptured
from the WP population. Five previously marked individ-
uals were ‘recaptured from the FHL population. Three
decreased in total length, and two increased. One of those
two had grown 0.5 mm in 287 days, indicating a growth
rate of less than 1 mm/yr. This individual was 11.9 mm
long when initially captured, however; and the larger in-
dividuals may grow more slowly than smaller ones, which
was a pattern seen in the other turrids examined from
these areas (SHIMEK, 1982, 1983).
In both populations, distinctly smaller animals were
recovered only in the spring. If this species has a faster
growth rate in the smaller size classes, the 4-6 mm-long
individuals recovered in the spring of one year may rep-
resent larvae settling the previous summer. Growth rate
determinations were difficult for these animals due to their
small size, the wide variation in lengths, and the lack of
more than one clearly defined peak in the size-frequency
histograms.
DISCUSSION
As with sympatric turrids in the genera Oenopota and
Ophiodermella, Kurtziella eats tube-dwelling polychaetes;
604 SPRING 1974
N= 45
me}
&
Oo
@
©
O
S
=
oe
N WINTER 1974-75 SUMMER 1975
= N=12 N= 21
3
e 40
ss
5 © 5 ye (© 05
Length (mm)
Figure 5
Friday Harbor Laboratories seasonal size-frequency distribu-
tions. In seasons not shown (Summer, 1974; Spring, 1975) too
few snails were observed to make the data meaningful.
but the range of prey taken is quite broad, from oweniids
to cirratulids, although at WP, Owenia predominates. The
diversity of acceptable prey may be less at WP, possibly
limiting animals in this population to fewer potential prey
species. This might also explain the tendency of the Kurt-
ziella to be found in areas where Owenia was common.
Because manipulative experiments were not attempted,
the turrid’s effect on its prey is uncertain, but predation
by Kurtziella alone probably did not have any substantial
impact on the populations of its prey. The species ap-
peared to have ample food sources; indeed, Tharyx mul-
tifilis, its major food, was one of the most abundant poly-
chaetes in the FHL areas, and Owenia fusiformis was very
abundant in some habitats at WP.
Kurtziella appears to be restricted to sandy or sandy-
mud habitats and is rarely found on nearby rocky or shell-
fragment habitats. Additionally, it seems to have substan-
tial latitude in potential prey, although more data are
needed to confirm this. The skewed distribution of Kurt-
ziella at WP may indicate tracking of its most common
prey species, Owenia fusiformis. Qwenia was rarely found
Rewer Shimek 1983
Page 17
below the upper-slope areas, and Kurtziella is more com-
mon in these upper areas than in the lower ones.
Predatory effects on this species are difficult to deter-
mine. The major predators in the WP area are inferred
to be the crabs, Cancer gracilis and C. productus. Both
crabs were common and have been shown to eat other,
larger, turrid gastropods in the same area (SHIMEK, 1982,
1983). Nonetheless, no direct evidence of this predation
was encountered. Kurtziella is a small snail with a rela-
tively fragile shell, and attacks by these large crabs prob-
ably result in the complete destruction of the shell. Unlike
Ophiodermella and Oenopota species, Kurtziella does not
show any significant tendency to bury; this may result in
substantial mortality when the predatory crabs are com-
mon. The relative rarity of the species at WP during and
after the summer population peak of the crabs is likely
the result of predation. The smaller mean length of in-
dividuals in the WP population, compared to the FHL
population may result from some size-selective predation
by the crabs on larger snails. Immigration from deeper
habitats where the crabs are less common is probably re-
sponsible for the recovery of the population.
Mortality effects at FHL are unknown. During the
course of study, over 100 turrid shells were recovered with
hermit crabs in them: These shells proved useful in de-
termining some of the causes of mortality of some of the
other turrids in the region (SHIMEK, 1982, 1983), but no
Kurtziella shells were recovered. This may be indirect evi-
dence of predation by crushing predators like crabs, which
can sometimes be found in the FHL habitat. Some fishes
may also eat the snails. Except for Luidia foliolata Grube,
1866, predatory asteroids are uncommon in the area.
In both populations, the snails appear to have a defined
maximum size of about 15 mm. Growth may cease or
slow as the animals approach this size, thus making mea-
surement of growth rates difficult. There is no indication
of semilparity in this species. After spawning, the females
appear healthy, and all were marked and returned to their
habitat.
In conclusion, Kurtziella requires sandy or sandy-mud
habitats, and overall is a dietary generalist, although it
may specialize in some populations. Thus, the hypothesis
that Kurtziella plumbea is a “ Jack-of-all-trades” for both
diet and habitat is rejected. It is likely that suitable sandy
or sandy-mud habitats are widespread on the Pacific coast
of North America; this turrid should be expected in many
of them. That this species will be rarely found in rocky
or shell-fragment areas is also predicted.
ACKNOWLEDGMENTS
Portions of this paper are taken from a dissertation sub-
mitted in partial fulfillment of the requirements for a Ph.D.
in the Department of Zoology at the University of Wash-
ington. Members of my graduate committee, particularly
Dr. Alan Kohn, Dr. Eugene Kozloff, Dr. Paul Illg, and
Dr. Ken Chew, made many helpful suggestions. The field
work for this study was done with SCUBA, and while I
cannot thank all 83 of my diving partners individually,
Paul Raymore, Carl Nyblade, Larry Moulton, Steve
Bloom, Ken Sebens, Kathy DeRiemer, and Ed DeMartini
were especially helpful.
The Pacific Northwest Shell Club, Elsie Marshall and
Hal Scheidt in particular, provided much information of
value in locating study sites.
I thank Dr. Robert Fernald and Dr. Dennis Willows,
directors, and Dr. Richard Strathmann and Dr. Eugene
Kozloff, acting directors, of the University of Washington
Friday Harbor Laboratories for allowing the use of facil-
ities.
Earlier drafts of this manuscript were read in part or
totally by A. Kohn, E. Kozloff, R. Paine, and R. Fred-
rickson, and two anonymous reviewers. I thank them all
for their helpful suggestions.
This work was partially supported by N.S.F. Grant
75-03303 to Dr. Kohn, by an N.S.F. doctoral dissertation
grant GA-41814, by grants from the Friday Harbor Lab-
oratories, and by two scholarships from the Pacific North-
west Shell Club.
A final special debt is owed to R. Fredrickson, for with-
out her help this work would not have been completed.
LITERATURE CITED
Buiss, C. I. 1967. Statistics in biology. Vol. 1. McGraw-Hill,
New York. 558 pp.
KEEN, A. M. 1971. Seashells of tropical west America. 2nd
ed. Stanford Univ. Press, Stanford, Calif. 1064 pp.
Koun A. J. & J. W. NyBAKKEN. 1975. Ecology of Conus on
eastern Indian Ocean fringing reefs: diversity of species and
resource utilization. Mar. Biol. 29:211-234.
SHIMEK, R. L. 1977. Resource utilization and natural history
of some northeastern Pacific Turridae. Doctoral thesis, Zo-
ology, University of Washington, Seattle.
SHIMEK, R. L. 1982. The biology of the northeastern Pacific
Turridae. I. Ophiodermella. Malacologia 23:281-312.
SHIMEK, R. L. 1983. The biology of the northeastern Pacific
Turridae. II. Oenopota. J. Molluscan Stud. (in press).
SOKAL, R. R. & F. J. ROHLF. 1969. Biometry. W. H. Free-
man, San Francisco. 776 pp.
Editor’s note: After the issue had gone to press, we
were informed that the paper referred to as “Shimek,
1982” throughout the present article was published in
1983.
The Veliger 26(1):18-21 (July 1, 1983)
THE VELIGER
© CMS, Inc., 1983
Flow Through and Around the Abalone
Haliotis kamtschatkana
by
JANICE VOLTZOW
Department of Zoology, Duke University, Durham, North Carolina 27706
Abstract.
Fluorescein dye streams released along the shell and at the shell openings of living and
dead abalones revealed the lines of water flow around and through the shell. Regardless of ambient
flow speed, water entered the shell of live abalones at a region to the left of the left cephalic tentacle
and also through the one or two most anterior shell openings and exited through the two or three most
posterior openings. An identical flow pattern occurred through the shell of dead, intact animals when
placed in an ambient flow of 6 cm/s, regardless of whether the anterior end faced upstream or down-
stream. Since the exhalent openings occur at the site of the shell at which the ambient streamlines are
maximally compressed, they experience a reduction in pressure relative to the anterior, inhalent ones.
Thus, the design of its shell may enable the abalone to take advantage of an induced flow to move
water more efficiently through its mantle cavity.
INTRODUCTION
Hahotis kamtschatkana Jonas, 1845, the pinto abalone, must
deal with changes in environmental flow while maintain-
ing respiratory currents through its mantle cavity. These
animals have a row of four to six openings through the
dorsal shell surface that, according to earlier workers
(GARSTANG, 1928; CROFTS, 1929; YONGE, 1947) evolved
to prevent wastes released in the mantle cavity from mov-
ing forward over the gills and head. In addition to creating
a flow through its shell by beating the cilia of its gills,
Haliotis could use environmental currents to help drive
water through its mantle cavity. Such an induced flow
requires that the inhalent openings encounter fluid at a
pressure higher than that of the exhalent openings (VOGEL,
1981). MuRbDock & VOGEL (1978) found that the keyhole
limpet, Diodora aspera, experiences such an externally
driven flow and may use this flow to move water more
efficiently through its mantle cavity. Haliotis kamtschat-
kana lives in areas of surge and strong currents (Richard
Emlet, personal communication), where it seems possible
that its series of shell openings could be exposed to pres-
sure differences sufficient for induced flow to occur. To
visualize the paths that lines of water flow follow around
and through abalones I combined information from dis-
sections, dye streams, and flow velocity measurements tak-
en in and around living and dead individuals.
MATERIALS anp METHODS
Five adult individuals of Haliotis kamtschatkana ranging
in maximum aperture diameter from about 9-12 cm and
collected from various sites in the Friday Harbor region
of San Juan Island, Washington were used. The flow
these animals normally encounter may range from 0-150
cm/s or more (Kenneth Collier, personal communication).
To relate the external flow information to the anatomy ~
of the animal, I dissected both fresh and narcotized ani-
mals. To narcotize, I added increasing volumes of a 7%
MgCl,-6H,0 solution to animals in cooled (8°C) sea water
until the epipodial and cephalic tentacles no longer re-
tracted when touched.
To visualize the flow of water qualitatively through and
around Haliotis kamtschatkana, | used a stream of fluores-
cein dye controlled by a micro dye injector (an adjustable
syringe fitted with a drawn plastic tip and moved by a
micromanipulator). Pencil marks at 1-cm intervals along
the edge of the shell served as reference points for follow-
ing dye paths, technically referred to as streaklines. Dye
was released at each of these points along both sides of
the animals as well as at various sites near the anterior
and dorsal surfaces of the shells. Studies of animals in
flowing and in still water took place in a 15-cm flow tank
designed by VOGEL & LABARBERA (1978).
Observations of induced flow were made on animals
J. Voltzow, 1983
Page 19
Borel eRe tye
rt
hata s
x
ae nie Se
1
PP aa cee
Figure 1
Diagram of flow through and around an abalone facing upstream in an ambient flow of about 6 cm/s. l.c.t.: left
cephalic tentacle; r.c.t.: right cephalic tentacle; m.t.: mantle tentacle; A: site at left side of shell where water enters
mantle cavity; 1, 2: anterior, inhalent shell openings; 3, 4, 5: posterior, exhalent shell openings; dot-dash lines
(—----): inhalent streaklines; dashed lines (— — —): exhalent streaklines; dotted lines (----- ): flow along anterior end
and side of shell. Letters and numbers at ends of exhalent streaklines correspond to the points at which streaklines
may have entered the mantle cavity.
that were first relaxed in MgCl, as above and then quickly
frozen to —20°C by placing them in the bottom of a cryo-
stat. The animals were returned to ambient sea water
temperature before any data were taken.
RESULTS
Dye released at specific points around an animal facing
upstream in an ambient flow of about 6 cm/s formed a
repeatable set of streaklines (Figure 1). Water approach-
ing the anterior edge of the shell was either deflected up-
ward (perpendicular to the general direction of flow),
straight upstream (180° to the general flow), or was passed
in a series of vortices along either side of the shell. Flow
contacting the shell at either side continued downstream
close along the shell and then became caught in the tur-
bulent backwash behind the animal. In ambient flows
ranging from approximately 2-15 cm/s the streaklines
did not appear to be velocity-sensitive, although there was
more turbulence at higher speeds.
Abalones accepted incoming water only at specific sites
along the shell (Figure 1: A, 1, 2). At the lower edge of
the shell, water entered in a region 1~3 cm to the left of
the left cephalic tentacle. It appeared that the animals
could control the entrance at this region by waving the
left cephalic tentacle. Dye released in the region between
the two cephalic tentacles sometimes traveled along the
edge of the shell, over the left tentacle and eye, and into
the mantle cavity. At other times under the same flow
conditions it was deflected by the tentacles and passed
downstream alongside the shell.
The two most anterior openings of the shell also served
as sites of water intake. Depending upon the position of
the mantle tentacles, dye released upstream, above, or be-
side these openings entered the mantle cavity. If the an-
terior opening was incomplete, resembling a fold at the
Page 20
The Veliger, Vol. 26, No. 1
edge of the shell, dye released just below its dorsal edge
proceeded into the mantle cavity, while dye released at
other points within the same region traveled up and out
away from the shell, as mentioned above.
Only the two or three most posterior openings on the
top of the shell served as the animals’ exhalent passages
from the mantle cavity. In all cases the penultimate open-
ing (4 in Figure 1), which ordinarily has no mantle ten-
tacle, was the chief channel for wastes and exhalent water
flow. The most posterior opening was often partially sealed
and always had a tentacle, both of which reduced its out-
put volume and rate. The center-most opening, which
usually had a mantle tentacle, tended to be weakly inhal-
ent, although at times dye streams also exited from it. Dye
streams usually exited from the posterior or from the right
side of the exhalent openings and were laminar.
Except at regions of exhalent and inhalent currents, dye
released at the sides of animals standing in still water did
not move. The inhalent and exhalent regions were at the
same locations in animals in still water as they were in
moving water.
Dye released at the inhalent openings of dead, intact
abalones facing upstream in a flow of about 10 cm/s en-
tered the mantle cavity at the site of release and exited
through one of the exhalent openings. Shells of the same
animals oriented downstream had similar patterns of flow
through them, although the rate of the induced flow was
not as high. In either orientation, dye released near ex-
halent openings did not enter the shell, but continued
downstream.
DISCUSSION
Although earlier reports indicated that water enters the
abalone mantle cavity only under the margin of the shell
and mantle flap on either side of the head (STEPHENSON,
1924; CRrorTs, 1929; YONGE, 1947), it is well known now
that in at least some species the first hole serves for water
intake as well (e.g., ABBOTT & HADERLIE, 1980, p. 233).
In Haliotis kamtschatkana the streaklines show that flow
enters the mantle cavity in a restricted region to the left
of the head and through the first, and sometimes second,
shell opening. Only the posterior openings are exhalent,
and they are the only channels by which water and ex-
cretory products may exit the mantle cavity.
The fact that the shell of a dead animal shows’ flow
patterns through its openings similar to those of a live
animal suggests that by its design, the animal may take
advantage of an induced flow. Because of the shell shape,
the exhalent openings lie in the region at which the
streamlines over the shell are maximally compressed,
leading to a reduction of pressure over the posterior open-
ings relative to the anterior ones, which should cause the
fluid to enter at the front and to exit at the rear (VOGEL,
1981). Location of openings relative to any wake formed
and the geometry of the openings may also determine local
pressure, but these aspects of flow were not investigated.
The orientation of the openings may further enhance
the induced flow. As openings form at the anterior edge
of the shell, they face the oncoming flow when the animal
is facing upstream, and thus encounter dynamic pressure,
or the pressure created due to stopping fluid (VOGEL,
1981). As the shell grows and new openings are added,
older openings rotate relative to a horizontal surface, be-
coming more nearly parallel to flow, so that by the time
they reach the central region of the shell and begin to
function as exhalent openings they experience the reduced
pressure described above. Thus as an animal grows, each
opening performs first an inhalent and later an exhalent
function. I noticed that on each animal there is one open-
ing (or sometimes two) that may be both slightly inhalent
near its anterior edge and exhalent near its posterior edge.
Such transitional openings are located on the cusp of the
shell and are oriented at an angle intermediate to openings
that are strongly inhalent or exhalent. It may be that there
is some angle at which an opening may no longer serve
as an entrance to, and another at which it may begin to
serve as an exit from, the mantle cavity. It is also possible
that the cephalic and mantle tentacles may valve the open-
ings and help control the direction and rate of flow.
Since induced flow may occur whether animals are fac-
ing upstream or downstream, they may need only be par-
allel to the general direction of surge to take advantage of
it. This would make induced flow useful in regions of
surge where flow reversal is common. It would be valuable
to know if abalones orient to flow in their natural habitat
and to what degree orientation is necessary for utilizing
induced flow.
Traditionally, workers have believed that the openings
in an abalone’s shell evolved primarily as a way to avoid
mixing fresh inhalent water with waste-laden exhalent
water. I have shown that in addition to eliminating this
problem, the shell determines the path by which water
will enter, as well as exit, the mantle cavity. Whether or
not this design increases the efficiency of moving water
through the mantle cavity will require a study of the en-
ergetics of water movement.
ACKNOWLEDGMENTS
This work began as a project for a course in biomechanics
taught by Dr. Steven Vogel and Dr. Michael LaBarbera
at the University of Washington’s Friday Harbor Labo-
ratories. I thank them for their generous supply of equip-
ment and encouragement. I also wish to thank the Pacific
Northwest Shell Club and Dr. Stephen Wainwright for
their support, and Vogel, Wainwright, and Dr. H. Fred-
erik Nijhout for commenting on the manuscript.
LITERATURE CITED
AppotTtT, D. P. & E. C. HADERLIE. 1980. Prosobranchia: ma-
rine snails. Jn: R. H. Morris, D. P. Abbott & E. C. Had-
erlie (eds.), Intertidal invertebrates of California. Stanford
Univ. Press, Stanford, Calif. pp. 230-307.
J. Voltzow, 1983
Crorts, D.R. 1929. Haliotis. Liverpool Mar. Biol. Com. Mem.
29:1-174.
GarsTaNnG, W. 1928. The origin and evolution of larval forms.
Brit. Assoc. Adv. Sci. Report of the 96th Meeting: pp. 77-
98.
Murpock, G. R. & S. VOGEL. 1978. Hydrodynamic induction
of water flow through a keyhole limpet (Gastropoda, Fis-
surellidae). Comp. Biochem. Physiol. 61A:227-231.
STEPHENSON, T. A. 1924. Notes on Haliotis tuberculata. J. Mar.
Biol. Assoc. U.K. 13:480-495.
Page 21
VoGEL, S. 1981. Life in moving fluids: the physical biology of
flow. Willard Grant Press, Boston, Mass. 352 pp.
VoGEL, S. & M. LABARBERA. 1978. Simple flow tanks for
research and teaching. BioScience 28:638-643.
YONGE, C.M. 1947. Pallial organs in aspidobranch gastropods
and their evolution throughout the Mollusca. Phil. Trans.
R. Soc. Lond. B 232:443-518.
The Veliger 26(1):22-25 (July 1, 1983)
THE VELIGER
© CMS, Inc., 1983
Shell Strength in Corbicula sp.
(Bivalvia: Corbiculidae) from the
Potomac River, Maryland
VICTOR S. KENNEDY
Horn Point Environmental Laboratories, University of Maryland,
Cambridge, Maryland 21613
JAY A. BLUNDON
Department of Zoology, University of Maryland, College Park, Maryland 20742
Abstract. Forces required to crack intact shells of the freshwater Asiatic clam, Corbicula sp., were
determined. They are higher than those which crack the wedge clam, Rangia cuneata, a globose, strong-
shelled, oligohaline bivalve. Asiatic clam shell shape and strength may explain published data on
crayfish predation on this animal in Oklahoma and Tennessee, in which predation was successful only
on clams less than 6 mm in size or those with holes in the shell. Strong shells may also help prevent
damage during periods of high river flow or strong water movement.
INTRODUCTION
CLAMS OF THE ASIATIC genus Corbicula were apparently
introduced to western North America early in this cen-
tury, becoming widespread in the ensuing years (BRITTON
& Morton, 1979; CounTs, 1981). Recently, laboratory
experiments by CovicH ef al. (1981) revealed that two
species of freshwater crayfish were able to feed only on
specimens of Corbicula that were less than 6 mm in size
or that had damaged (perforated) shells. The Asiatic clam
is globose in shape and the shell is relatively thick, giving
the impression of strength. MACKIE (1978) noted that the
thickness of the shell of Corbicula fluminea was greater
than the shells of 22 other species of sphaeriacean bivalves
he investigated.
In an earlier study of crustacean predation on estuarine
bivalves, we examined shell strength of eight species of
clams (BLUNDON & KENNEDY, 1982). Here we present
measurements of shell strength of the Asiatic clam, com-
pare them with the strength of the estuarine bivalves, and
relate the results to the findings of CovicH et al. (1981)
concerning crayfish predation on Corbicula.
TAXONOMY oF EXPERIMENTAL
ANIMALS
There has been much confusion associated with the tax-
onomy of Corbicula in North America, with BRITTON &
Mor Ton (1979) having declared the species to be Corbic-
ula fluminea. However, HILLIS & PATTON (1982) have
presented evidence that two species of Corbicula (a “white
form” and a “purple form’) are present in the Brazos
River, Texas. The specimens we tested in this report re-
sembled the “white form” in color of nacre. Our speci-
mens were collected from the Potomac River at Whites
Ferry, Maryland (approximately 39°09’N; 77°31’W) in
shallow water close to the river bank, a habitat in which
HILuis & PATTON (1982) found the “white form” to pre-
dominate. However, the mean number of growth rings
(“annuli”) for our sample was less than for the Texas
sample and, when number of annuli was plotted against
shell mass for each clam, all our values fell below the
“envelope” surrounding the values that HILLIs & PATTON
(1982) derived (their Figure 1) for the “white form” in
Texas.
V.S. Kennedy & J. A. Blundon, 1983 Page 23
400
300
200
o
Cc .
ro) Corbicula sp.
eel logY=1.96 log X-0.30
c
uJ
2 86
3 log Y= 2.31
Le
Rangia cuneata
log Y= 2.42 log X -1.73 —~>
10
| 5 10 20 30 40 50
LENGTH (mm)
Figure 1
Predictive regression ( ) and geometric mean functional regressions (----- ) for shell strength of Asiatic clam
(Corbicula sp.) and wedge clam (Rangia cuneata) from Maryland. Wedge clam data are from BLUNDON & KENNEDY
(1982).
We agree with HILLIs & PATTON (1982) that the as-
signment of a species name to populations of Corbicula is
unwarranted until conclusive taxonomic studies are per-
formed; thus we have called our bivalves Corbicula sp. in
this report. In referring to the reported work of others,
we have kept the species names they used. Specimens from
our study population have been deposited with the Smith-
sonian Institution’s National Museum of Natural History
(USNM 804414).
METHODS
To test for shell strength, we used an Instron testing ma-
chine, an industrial instrument that measures compression
applied to a surface (BLUNDON & KENNEDY, 1982). Clams
were crushed with a steel bar, 11 mm in diameter, which
moved vertically downward at a velocity of 4 mm/s. Clams
were crushed in the umbo region, parallel to the dorso-
ventral axis. A chart recorder was used to record force (in
newtons) required to crack the clam shell. A 10-newton
weight was used to calibrate the Instron before and during
the experiment. Clams for crushing were collected from
Whites Ferry and were crushed immediately upon return
to the laboratory (within 2 h of collection).
RESULTS
Initially, log,, force (Y) was regressed on log,, length (X),
length being the maximum anterior—posterior axis in mm,
and a regression line (log Y = 1.96 log X — 0.30) was
fitted (Figure 1). The coefficient of determination, R?, was
equal to 0.73 (n = 70). Because the measurements of force
and size are subject to error of measurement, a geometric
mean estimate of the functional regression may be a more
appropriate linear regression (RICKER, 1973). The resul-
tant equation (Figure 1) is: log Y = 2.31 log X — 0.76.
This curve is significantly different from zero (P < 0.001).
As a comparison with these data, the geometric mean
Page 24
regression for Rangia cuneata, an oligohaline bivalve res-
ident in Chesapeake Bay, is presented in Figure 1. Rangia
cuneata, like the Asiatic clam, is a globose bivalve with a
thick shell and closely fitting valves. It was the strongest
bivalve we tested in our survey of shell strength of eight
estuarine bivalves (BLUNDON & KENNEDY, 1982). How-
ever, the Asiatic clam had a stronger shell than did R.
cuneata (Figure 1). The slopes of the geometric mean
regression for the two species were not significantly dif-
ferent (P > 0.05), according to the test statistic of CLARKE
(1980). However, the elevations of the two curves were
significantly different (P < 0.001), as determined by Ho-
telling’s T? (MorRISON, 1967).
DISCUSSION
As noted earlier, MACKIE (1978) found that the shell of
Corbicula fluminea was the thickest of the shells of 23
species of sphaeriacean clams he studied. Neither MACKIE
(1978) nor CoUNTs & PREZANT (1982) present evidence
that the shell of Corbicula fluminea is unusual in its struc-
tural material or in the arrangement of that material. In
addition to shell thickness, the globose shape of the Asiatic
clam, like Rangia cuneata, is probably an important reason
for the crushing resistance being so high.
CovicH et al. (1981) noted that freshwater crayfish,
Procambarus clarkiu, attacked the edge of the shell of Asiat-
ic clams with their mandibles. Repeated chipping of the
shell led to eventual penetration. Such chipping away at
shell edges should allow a relatively weak predator to
open a strong-shelled bivalve. This chipping method was
successful only with clams less than 6 mm long. Asiatic
clams greater than 6 mm were successfully preyed upon
by the crayfish Cambarus bartoni if the clams had suffered
damage, such as perforations in the shell, which allowed
the crayfish to reach their first walking leg into the soft
clam body.
BROWN et al. (1979) found that a 33.7-g specimen of
Procambarus clarku could exert an average force of 9.9
newtons in the region of the base of the chelipeds, with
force decreasing to 3.4 newtons near the tip of the che-
lipeds. The P. clarkit used by Covicu et al. (1981) ranged
in size from 21.0-34.6 g, averaging 27.8 g. Using our
geometric mean regression equation, we find that a 4-mm
and 6-mm long Asiatic clam (respectively, the minimum
and maximum size of undamaged prey that P. clarki
opened, according to COVICH et al., 1981) have an average
shell strength of about 4 newtons (4-mm clam) to 11 new-
tons (6-mm clam). Thus, if our data are transferable to
southern clams, the crayfish used by CovIcH et al. (1981)
may not have been able to crush the Asiatic clams greater
than 6 mm long, even if they had used their chelipeds in
a crushing attempt (Covich et al. do not report any at-
tempts by P. clarki to use their chelae to crush shells).
The Veliger; VoljZoyiNowm
Theoretically, the larger crayfish (e.g., 34.6 g) could crush
the smallest (4 mm) clams available, assuming that the
chelae could grip the globose shell appropriately.
With regard to other sources of shell damage that might
leave Asiatic clams susceptible to crayfish predation, our
clams were collected from a substrate of gravel and peb-
bles covered with silt, with cobble stones and boulders also
present. Fast river flow during floods (e.g., in spring) might
cause substrate movement, with tumbling of clams or rocks
and with grinding and pressure on shells. Strong shell
structure would seem a useful protective measure under
such conditions. CovicH et al. (1981) found damaged
(perforated) shells in a rocky region of variable water flow
below a dam. We have not noted much broken or damaged
shell in our monthly surveys of Asiatic clams in our col-
lecting area; most dead shell has consisted of intact valves.
We conclude that the thickness and globose shape of
the shell of the Asiatic clam, which probably accounts for
its considerable strength, should provide protection from
predator crushing attack, especially for larger clams. This
strength may also protect the clams in situations where
they, or rocks, are being tumbled about in fast-flowing
waters.
ACKNOWLEDGMENTS
Partial support for this research was provided by Power
Plant Siting Program Contract P87-82-04 from the
Maryland Department of Natural Resources. We ac-
knowledge the assistance of Laurie Van Heukelem. Deb-
orah Kennedy drew Figure 1. Contribution No.
1378HPEL of the Center for Environmental and Estua-
rine Studies.
LITERATURE CITED
BLUNDON, J. A. & V. S. KENNEDY. 1982. Mechanical and
behavioral aspects of blue crab (Callinectes sapidus Rathbun)
predation on Chesapeake Bay bivalves. J. Exp. Mar. Biol.
Ecol. 65:47-65.
BRITTON, J. C. & B. Morton. 1979. Corbicula in North
America: the evidence reviewed and evaluated. Jn: J. C.
Britton (ed.), Proceedings, First International Corbicula
Symposium. pp. 249-287.
Brown, S. C., S. R. Cassuto & R. W. Loos. 1979. Biome-
chanics of chelipeds in some decapod crustaceans. J. Zool.
(Lond.) 188:143-159.
CLARKE, M. R. B. 1980. The reduced major axis of a bivariate
sample. Biometrika 67:441-446.
Counts, C. L. 1981. Corbicula fluminea (Miiller) on the Del-
marva Peninsula. Veliger 24:187-188.
Counts, C. L. & R. S. PREZANT. 1982. Shell microstructure
of Corbicula fluminea (Bivalvia:Corbiculidae). Nautilus 96:
25-30.
Covicu, A. P., L. L. DyE & J. S. Mattice. 1981. Crayfish
predation on Corbicula under laboratory conditions. Am.
Mid]. Nat. 105:181-188.
Hiuis, D. M. & J. C. Patron. 1982. Morphological and
electrophoretic evidence for two species of Corbicula (Bival-
V.S. Kennedy & J. A. Blundon, 1983 Page 25
via: Corbiculidae) in North America. Am. Midl. Nat. 108: Morrison, D. F. 1967. Multivariate statistical methods.
75-80. McGraw-Hill, New York. 338 pp.
Mackig, G. L. 1978. Shell structure in freshwater Sphaerea- Ricker, W. E. 1973. Linear regressions in fishery research.
cea (Bivalvia:Heterodonta). Can. J. Zool. 56:1-6. J. Fish. Res. Board Can. 30:409-434.
The Veliger 26(1):26-29 (July 1, 1983)
THE VELIGER
© CMS, Inc., 1983
Relationship Between Beak Morphometrics and
Live Wet Weight of the Giant Pacific Octopus,
Octopus dofleint martini (Wiilker)
by
SHAWN M. C. ROBINSON anp E. BRIAN HARTWICK
Department of Biological Sciences, Simon Fraser University,
Burnaby, British Columbia, Canada V5A 1S6
Abstract.
Twelve separate beak measurements were taken on 73 different sets of beaks and a
relationship was established with the live weight of Octopus doflein: martin: (Wiilker). The pigment
upper-lateral-wall length best predicted the weight of the octopus after taking the natural logarithm of
each measurement. Pigment lengths were found to be slightly more accurate than the corresponding
total lengths. We could find no set of measurements which would permit discrimination between sexes
based on beak morphometrics.
INTRODUCTION
THE HORNY MANDIBLES, called beaks, found within the
buccal mass of cephalopods have received attention for a
number of different reasons. There has been considerable
interest in their function during feeding (ALTMAN &
Nixon, 1970), the organization of their movements (BOYLE
et al., 1979a, b) and their potential in taxonomic work
(CLARKE, 1962a, b; AKIMUSHKIN, 1965; MANGOLD &
FIORONI, 1966; CLARKE & MacLEop, 1980; IVERSON &
PINKAS, 1971). Studies also indicate the possibility of us-
ing beak measurements to estimate cephalopod body size
(CLARKE, 1962b; Nixon, 1969, 1973) and in the case of
the squid Illex illecebrosus to differentiate between sexes
(MERCER ef al., 1980).
The ability to identify cephalopods by their beaks and
to estimate their size from measurements of these hard
parts provides considerable opportunity to extract infor-
mation from stomach analyses of marine predators. Such
information includes indications of predator migratory
patterns (CLARKE & STEVENS, 1974), predator diet (see,
for example, PITCHER, 1981; RANDALL et al., 1981), ceph-
alopod distribution (CLARKE, 1962c), and the relative im-
portance of cephalopods in the ecology of the oceans
(CLARKE, 1977). Clarke’s report of 18,000 beaks in the
stomach of one sperm whale gives some impression of
their importance to these marine mammals.
Much of the work on beaks has centered on various
species of squids, although NIxon (1969, 1973) has car-
ried out studies on Octopus vulgaris beaks. No information
is available on beaks of the giant Pacific octopus, Octopus
dofleini, although a brief description is given by WINKLER
& ASHLEY (1954) and PICKFORD (1964). Pickford de-
scribes possible growth lines on beaks and records rostral
length indices for this species.
Octopus dofleint martin: is an abundant, fast-growing
form inhabiting the coastal waters of British Columbia
and extending as far south as California. Its current sta-
tus, as a candidate for fisheries development (HARTWICK
et al., 1978), means that information on its distribution,
mortality and predator-prey size relationships is desirable.
Since examination of beaks may provide such information,
an attempt was made to measure a series of beak dimen-
sions and to relate these to body size and sex.
MATERIALS anp METHODS
During May, 1981, to February, 1982, 73 animals (15
males, 58 females) were captured in Clayoquot Sound on
the west coast of Vancouver Island, British Columbia.
SCUBA was used to collect the octopuses, and the first
animals encountered were captured and taken to a vessel
at the surface. After draining the mantle cavities, live wet
weights were taken using spring scales sensitive to 0.25
kg for animals over 3 kg and 0.025 kg for animals less
than 3 kg. The entire buccal mass was then removed from
the animal and stored in 10% formalin in seawater. Later,
beaks were gently excised from the surrounding muscle
S. M. C. Robinson & E. B. Hartwick, 1983
Page 27
UPPER BEAK
1-UHL
2-PUCL
3-TUCL
4-PULWL
5- URW
LOWER BEAK
6-LHL
7-PLWL
8-TLWL
9-TSLWL
10-PLCL
11-TLCL
12-LRW
Figure 1
Measurements taken on upper and lower beaks of Octopus do-
fleini.
tissues and measured, using Vernier calipers, to the near-
est 0.05 mm. Twelve measurements per beak were taken
using terminology modified from CLARKE (1962b). As the
octopus grows, new chitin is added to the edge of the
wings, crest, and lateral wall (NIxon, 1969). This leaves
a translucent margin on the edges where it has not become
dark and horny. The interface of this translucent area
with the pigment is used for the measurement of the pig-
ment length. The measurements taken were: pigment up-
per-crest length (PUCL), pigment lower-crest length
(PLCL), pigment upper-lateral-wall length (PULWL),
pigment lower-wing length (PLWL), total upper-crest
length (TUCL), total lower-crest length (TLCL), total
lower-wing length (TLWL), total standard-lower-wing
length (TSLWL), upper hood length (UHL), lower hood
length (LHL), upper rostral width (URW), and lower
rostral width (LRW) (Figure 1).
Analysis of the data was carried out using least-squares
regression and discriminant analysis, both statistical com-
puter package programs (MIDAS). Correlation tests were
taken from SOKAL & ROHLF (1969, p. 521).
RESULTS anp DISCUSSION
In this study, we attempted to predict the live wet weight
of the octopus from the beak measurements. This was
chosen over other measurements, such as the dorsal man-
tle length, since body weight seems to be a more accurate
measurement of size than length in live material (NIXON,
1968). The weight range of animals measured was from
Table 1
Regression statistics of the natural logarithm of beak mea-
surements (mm) versus the natural logarithm of live wet
weight (kg) for Octopus dofleini (n = 73). (r = correlation
coefhicient; SE = standard error of regression; m = slope;
b = y-intercept.)
Measurement Toa SE m 19)
In PULWL 0.970 0.044 0.274 2.674
In PLWL 0.967 0.045 0.265 2.969
In PUCL 0.965 0.048 0.277 B22
In PLCL 0.959 0.050 0.268 DO
In TLWL 0.946 0.053 0.245 3.074
In TSLWL 0.938 0.058 0.248 2.926
In TUCL 0.934 0.060 0.247 BATS
In TLCL 0.927 0.068 0.264 2.832
In UHL 0.921 0.061 0.228 2.382
In LHL 0.909 0.074 0.253 1.954
In URW 0.885 0.082 0.244 1.216
In LRW 0.784 E13) 0.261 1.059
* All r’s are highly significant at the 99% confidence level.
0.95 to 22.75 kg with a mean weight of 7.64 kg. There
was a non-linear increasing function of beak measure-
ments on wet weight so the natural logarithms of both
axes were taken in order to obtain a linear function. A
transformation to the cube root of the live wet weight was
also attempted, to test whether a better fit of the data to
a line was obtained, but the fit was not as good as taking
the natural logarithm of both axes.
The relationships between the twelve measurements on
the upper and lower beaks may be seen in Table 1. It is
apparent from this table that all the beak measurements
are good predictors of octopus weight with the correlation
coefficients (r) ranging from 0.784 to 0.970. Although the
best measurement is the pigment upper-lateral-wall length
(PULWL), shown in Figure 2, there is really very little
difference among the first three measurements. All of the
beak measurements in Table 1 have been grouped from
the highest correlation coefficient to the lowest and this
resulting hierarchy allows one to choose the best mea-
surement that is available. A hierarchy of possible mea-
Table 2
Significance of the correlation coefficient values between
corresponding pigment and total length beak measure-
ments (Fisher’s z transformation).
Comparison
1 vs. 2 n z(1) z(2) IP <<
In PUCL In TUCL if 2.0191 1.6902 0.052
In PLCL In TLCL 73 1.9345 1.6376 0.080
In PLWL In TLWL 73 2.0484 1.7943 0.133
Page 28
3.6
An
A
A
3.45 Ae
3.2-
A
In Pigment Upper Lateral Wall Length (mm)
2.87
OA
A
205 = Th Rae sa
= 0 1 2 3 4
In Octopus Weight (Kg)
Figure 2
The relationship between pigment upper-lateral-wall length and
live wet weight of Octopus dofleini (natural logarithms of both
axes).
surements would be advantageous if only one of the beaks
was available and/or it was damaged in some way neces-
sitating an alternate measurement.
Our results compare favorably with those of NIXON
(1973) with Octopus vulgaris. She found that after boiling
the beaks in a 5% potassium hydroxide solution to remove
the surrounding muscle tissue, there was a high degree of
correlation (r = 0.97 with n = 77) between the logarithm
of live wet weight and the logarithm of crest length of the
upper beak. It is interesting to note that the correlation
coefficient for the pigment upper-crest length (PUCL) in
our study is essentially the same as Nixon’s with approx-
imately the same number of samples taken, and that an
upper-beak measurement is generally more accurate in
predicting weight than its corresponding one on the lower
beak.
In our study, essentially two types of measurements
were made: pigment lengths and total lengths, although
four measurements—UHL, LHL, URW, and LRW—
were not readily assignable to either of these. As can be
seen from Table 1, there is a distinct grouping of mea-
surements with the pigment lengths in every case having
higher correlation coefficients than the total lengths. To
The Veliger, Vol. 26, No. 1
determine whether a significant difference existed between
these two types of measurements, Fisher’s z-transforma-
tion test was carried out (Table 2). Three sets of corre-
sponding measurements were used, and the data show that
there is only a slightly significant difference between them
(ranging from P < 0.05 to P < 0.13). Despite the low
levels of significance, the use of pigment lengths over total
lengths is warranted by the fact that often the delicate
translucent edge will be destroyed if the beak is not care-
fully removed from the muscle tissue of the buccal mass.
Although MERCER et al. (1980) were able to differen-
tiate between sexes of the squid Illex illecebrosus using
beak morphometrics in a discriminant analysis, our at-
tempts to find a set of beak measurements in Octopus
dofleint which would separate sexes using this technique
were unsuccessful. Although this may have been due, in
part, to a small sample size of males, there was a large
degree of overlap between the generated male and female
discriminant values.
ACKNOWLEDGMENTS
This work was supported by a National Sciences and
Engineering Research Council grant and a Canada Fish-
eries and Oceans grant to E. B. Hartwick. We gratefully
acknowledge the help of D. Trotter, L. Tulloch, M. Walsh,
and G. Cox for their valuable assistance in the field and
to R. Lockhart for his advice with the analysis.
LITERATURE CITED
AKIMUSHKIN, I. I. 1965. Cephalopods of the seas of the USSR.
Translation of 1963 Russian edition by A. Mercado, Je-
rusalem. 223 pp.
ALTMAN, J. S. & M. Nixon. 1970. Use of beaks and radula
by Octopus vulgaris in feeding. J. Zool. (Lond.) 161:25-38.
BoyLeE, P. R., K. MANGOLD & D. FROESCH. 1979a. The man-
dibular movements of Octopus vulgaris. J. Zool. (Lond.) 188:
53-67.
Boy.e, P. R., K. MANGOLD & D. FROESCH. 1979b. The or-
ganization of beak movements in Octopus. Malacologia 18:
423-430.
CLARKE, M. R. 1962a. Significance of cephalopod beaks. Na-
ture 193:560-561.
CLARKE, M.R. 1962b. The identification of cephalopod “beaks”
and the relationship between beak size and total body weight.
Bull. Br. Mus. (Nat. Hist.) 8:419-480.
CLARKE, M. R. 1962c. The identification of cephalopod beaks
and their significance in systematic and ecological studies of
squids and their predators. Rep. Challenger Soc. 3(14):43-
44.
CiarkE, M. R. 1977. Beaks, nets and numbers. Symp. Zool.
Soc. Lond. 38:89-126.
CriarkE, M. R. & N. MacLeop. 1980. Cephalopod remains
from sperm whales caught off western Canada. Mar. Biol.
59(4):241.
CLARKE, M. R. & J. D. STEVENS. 1974. Cephalopods, blue
sharks and migration. J. Mar. Biol. Assoc. U.K. 54:949-
957.
Hartwick, E. B., P. A. BREEN & L. TULLOCH. 1978. A re-
moval experiment with Octopus dofleini (Wiilker). J. Fish.
Res. Board Can. 35(11):1492-1495.
S. M. C. Robinson & E. B. Hartwick, 1983
Page 29
Iverson, I. L. K. & L. Pinkas. 1971. A pictorial guide to
beaks of certain eastern Pacific cephalopods. Calif. Dep.
Fish. Game, Fish Bull. 152:83-105.
MANGOLD, K. & P. FIORONI. 1966. Morphologie et biométrie
des mandibules de quelques céphalopodes Méditerranéens.
Vie et Milieu 17:1139-1196.
Mercer, M. C., R. K. Misra & G. V. Hurvey. 1980. Sex
determination of the ommastrephid squid Illex ilecebrosus
using beak morphometrics. Can. J. Fish. Aquat. Sci. 37:
283-286.
Nixon, M. 1968. Growth of radula in Octopus vulgaris. J.
Physiol. (Lond.) 196:28P-30P.
Nixon, M. 1969. Growth of the beak and radula of Octopus
vulgaris. J. Zool. (Lond.) 159:363-379.
Nixon, M. 1973. Beak and radula growth in Octopus vulgaris.
J. Zool. (Lond.) 170:451-462.
PICKFORD, G. E. 1964. Octopus dofleini (Wiilker). Bull. Bing-
ham Oceanogr. Coll. 19(1):1-70.
PircHer, K. W. 1981. Prey of the Steller sea lion, Eumetopias
jubatus, in the Gulf of Alaska. U.S. Nat. Mar. Fish. Serv.
Fish. Bull. 79(3):467-472.
RANDALL, R. M., B. M. RANDALL & E. W. KLINGELHOEFFER.
1981. Species diversity and size ranges of cephalopods in
the diet of jackass penguins from Algoa Bay, South Africa.
S. Afr. J. Zool. 16(3):163-166.
SOKAL, R. R. & F. J. ROHLF. 1969. Biometry. W. H. Free-
man, San Francisco. 776 pp.
WINKLER, L. R. & L. H. ASHLEY. 1954. The anatomy of the
common octopus of northern Washington. Walla Walla Coll.
Publ. Biol. Sci. Number 10 (November 10, 1954).
The Veliger 26(1):30-36 (July 1, 1983)
THE VELIGER
© CMS, Inc., 1983
Studies on the Reproductive Biology of Some
Prosobranchs from the Coast of Pakistan Bordering
the Northern Arabian Sea. II]. Egg Capsules and
Larvae of Four Species of Thais
SOHAIL BARKATI anp MUZAMMIL AHMED
Institute of Marine Biology, University of Karachi, Karachi-32, Pakistan
Abstract. Egg masses of four species of Thais, namely, 7. rudolphi, T. carinifera, T. bufo, and T.
tissoti, are reported from the coast of Pakistan for the first time. Based on the incidence of their egg
capsules, the respective breeding seasons of the four species are: June to September, February to
November, April to August, and March to August. The four species deposit benthic egg capsules from
which free-swimming veligers are hatched. A comparative account of numbers and dimensions of
capsules, number and sizes of eggs, and developmental periods of shelled larvae is presented.
INTRODUCTION
THE EGG MASSES and capsules of prosobranch mollusks,
apart from the fact that they are of scientific interest in
themselves, yield information about the breeding seasons
of the parent species, may prove of assistance in the precise
identification of closely related species, and provide larval
stages and juveniles should there be a need for their com-
mercial rearing. Although the literature in this field is
vast, only the following are the major publications on the
gastropods of the Arabian Sea: (THORSON (1940) from the
Persian Gulf; NATARAJAN (1957) from the Gulf of Ma-
nnar and Palk Bay; GOHAR & EISAWAY (1962, 1967a, b)
from the Red Sea; and DEsal (1962), GANAPATI & SASTRY
(1973), RAMAMOORTHY & NATARAJAN (1973), and Ka-
SINATHAN et al. (1974) from different parts of the Indian
coast. No information is available on the egg masses and
larval development of marine gastropods from the coast of
Pakistan bordering the northern Arabian Sea. It was in
view of this paucity of information that a project was
initiated in 1976 at the Institute of Marine Biology, Uni-
versity of Karachi, to study the same. Observations on the
juveniles of the gastropod Planaxis sulcatus from the coast
of Karachi have already been published (BARKATI &
AHMED, 1982). The present report on four species of Thazs
is the second in the series.
MATERIAL anp METHODS
In order to collect egg masses and capsules of local gas-
tropods, regular biweekly visits were made during the
period June, 1976, to July, 1977, to Buleji, which is a
rocky and partly sandy-cum-muddy beach about 18 km
northwest of Karachi. Egg capsules were also collected
rather irregularly from some other beaches in the Karachi
area, namely, Manora Island, Keamari Seawall, Paradise
Point, and Korangi Creek, and from Gawader and Jiwani
on the Mekran coast, about 600 km northwest of Karachi.
Some egg capsules had been collected prior to June, 1976,
and others after July, 1977. Except for a couple of rainy
months in summer the salinity at all these sites is high,
ranging from 36-40%. In most of the cases the spawning
female snails were present near their egg masses. It was
difficult to ascertain the number of egg capsules spawned
by individual snails since the capsules are laid together.
During the study, therefore, only representative samples
of egg capsules were collected although some of these con-
sisted of the entire lots of capsules spawned by individual
snails.
Attempts to spawn specimens of the different species of
Thais in the laboratory in limited quantities of water did
not succeed. The egg capsules, and the larvae hatching
from these, were maintained in filtered and aerated sea
S. Barkati & M. Ahmed, 1983
Page 31
water in 1600-ml glass bowls. They were fixed in 5%
formalin and then preserved in 70% ethanol for subse-
quent study. Measurements of the size of capsules, eggs,
and larvae were made with an ocular micrometer on a
microscope. Illustrations were prepared with a camera
lucida.
OBSERVATIONS
Breeding Season
The four species of Thais investigated occur near the
low and mid-tidal zones of the rocky beaches of the coast
of Pakistan. The number of egg masses of four species
collected from different localities is given in Table 1. It is
apparent from this table that 7. rudolphi (Lamarck)
spawns from June to September, 7. tissot: (Petit) from
March to August, and 7. bufo (Lamarck) from April to
August. An egg mass of 7. carinifera (Lamarck) was taken
at station 45 (63°46/N latitude) along the Mekran coast
on March 1, 1977, in a purse seine haul of the Norwegian
Fisheries Research Vessel “Dr. Fridtjof Nansen” (egg
capsules of this species in THORSON’s [1940] collection
from the Persian Gulf were obtained from a depth of 11-
22 m). Since some of the capsules in this egg mass were
of purple color they must have been spawned in February.
Recently, an egg mass of 7. carinifera was also collected
from Port Qasim, about 30 km southeast of Karachi. The
spawning season of 7. carinifera on the coast of Pakistan,
therefore, seems to extend from February to November.
Characteristics of Egg Capsules,
Eggs, and Larvae
Egg capsules of 7. rudolphi (Figure 1A, B), like those
of other species of Thais, are creamy white in color when
deposited and become dark gray with the advancement of
embryonic development. A change in color from yellow to
gray was also observed by NATARAJAN (1957) in 7. bufo.
The capsules are deposited in clusters of several irregular,
short rows imparting a circular shape to the egg mass in
general. There is always one layer of capsules the basal
plates of which unite to form a common basal membrane
that is firmly glued to the substratum. Each capsule has
translucent, tough leathery walls. An aperture for the re-
lease of larvae, 0.32 mm in diameter, is present slightly
off center on the flattened, apical surface of each capsule
and is covered with a transparent membrane which rup-
tures at the time of larval hatching. Dimensions of cap-
sules, eggs, and larvae of this species are given in Table
2. The larvae just after hatching (Figure 1C, D) possessed
shell lengths of 211 to 251 um and widths of 171 to 182
um. They swam actively and gathered near the walls of
the glass bowls. Their shells consisted of one and a half
whorls. They measured 353 to 376 wm in height and 274
to 285 wm in width 36 h after hatching.
The egg mass of 7. carinifera consists of closely spaced,
stalkless, somewhat curved and thin tubular capsules that
Table 1
The incidence of egg masses of four species of Thais on
the coast of Pakistan. Exposure of shore abbreviated as:
Exposed, E; Protected, P; Semi-exposed, SE; Subtidal,
ST.
Expo- Egg
Locality sure Date Year masses
T. rudolphi
Manora Island E June 9 1970 Many
Buleji E June 15 1976 1
Manora Island E June 16 1976 2
Buleji IE; July 2 1976 2
Buleji E July 3 1977 4
Buleji E August 13 1976 1
Paradise Point E August 26 1975 1
Buleji E September 8 1975 1
Buleji E September 9 1976 2
Paradise Point E September 9 1976 1
T. carinifera
Mekran Coast ST March 1 1977 1
Jiwani SE April 29 1979 g
Korangi Creek P April 30 1978 1
Native Jetty le May 1972 Many
Buleji E June 14 1980 1
Keamari Seawall 1? August 1 1976 3
Port Qasim P November 1 1982 1
T. tissot
Sandspit Bridge P March 16 1979 1
Jiwani SE April 29 1979 2
Korangi Creek P April 30 1978 1
Buleji SE June 4 1980 1
Manora Island E June 9 1970 Many
Keamari Seawall rR August 1 1976 1
Korangi Creek 12 August 21 1977 Many
T. bufo
Jiwani SE April 29 1979 1
Keamari Seawall P May 1975 3
Keamari Seawall P May 18 1976 1
Manora Island E June 9 1970 Many
Keamari Seawall P June 13 1975 1
Manora Island E June 13 1979 1
Keamari Seawall P August 1 1976 1
have very smooth translucent walls without any ridges
(Figure 2A, B). They are of uniform width but taper at
the apex to form a nipple-like structure. The apex func-
tions as an operculum which is shed at the time of hatch-
ing so as to provide an exit for the larvae. This aperture
is 0.4 mm in diameter. Dimensions of capsules, eggs, and
larvae of this species are given in Table 2. The larvae 12
h after hatching (Figure 2C, D) measured 388 X 295 um.
Their shell walls were smooth and transparent and con-
sisted of one and a half whorls. They attained a size of
401 X 301 wm (Figure 2E) after 36 h of development.
Very few larvae survived in the laboratory for 60 h with-
out food. The egg mass of 7. carinifera was described
Page 32
The Veliger, Vol. 26, No. 1
Figure 1
Thais rudolphi: A. dorsolateral view of a portion of an egg mass; B. dorsolateral view of an egg capsule; C. ventral
view of a larval shell just after hatching; D. dorsal view of the same; E. ventral view of 36-h larval shell.
earlier by ANNANDALE & Kemp (1916) from Chilka Lake,
India, and by THORSON (1940) from the Red Sea. Na-
TARAJAN (1957) also described an egg mass that closely
fits the above description but he was not able to assign it
to any species.
Egg capsules of 7. tissot: are stalkless (Figure 3A, B)
and attach themselves to the substratum by their basal
plates, which unite to form a basal membrane. The cap-
sules are smaller than those of 7. carinifera. They are
cylindrical, somewhat broader in the middle, taper at both
ends, and curve on one side. Their walls are smooth and
without ridges. A preformed aperture for the release of
larvae does not exist but the apex of the capsule sheds off
at the time of hatching. The part shed measures 0:72 X
0.32 mm across. Dimensions of capsules, eggs, and larvae
of this species are given in Table 2. The larval shell (Fig-
ure 3C) soon after hatching consists of one and a half
whorls. Changes in the size of the larval shell of this
species with time are shown in Table 3. The larvae thrived
in the laboratory without food for about nine days but
showed very little increase in shell dimensions after 84 h.
The maximum shell dimensions recorded were: height 467
pm and width 456 um.
The capsules of 7. bufo (Figure 4A, B, C) have smooth
and very thick walls, are tubular in shape, and have long
thin stalks which unite at the base and are glued to the
substratum. The proximal end of the capsules is swollen
and carries a rounded aperture for the exit of larvae. The
aperture measures 0.49 to 0.58 mm in diameter and is
covered by a thin membrane. The larvae (Figure 4D, E)
hatch from the capsules as free-swimming veligers. Their
dimensions appear in Table 2.
The egg mass of 7. bufo was earlier described from
south Indian waters by Gravely (1942, in NATARAJAN,
1957), Chari (1950, in NATARAJAN, 1957) and by Na-
TARAJAN (1957) and the above account describes it closely.
An egg mass was collected from the bottom of a crevice
of a steep rocky ledge at Paradise Point that might be
from a fifth species of Thais (or another muricid). This
ball-like egg mass measured 2.4 X 2.2 cm across and con-
sisted of two layers of low rounded and irregularly shaped
capsules which were stalkless, with their basal plates united
to form a common membrane.
DISCUSSION
Observations made during the present study show that
three of the four species of 7hais examined, namely, 7.
bufo, T. tassoti, and T. carinifera, spawn for about six to
seven months in the spring and summer during the period
February to August, whereas 7. rudolphi has the shortest
spawning season of four months, restricted to the summer
months of June to September. There is evidence that
spawning in at least two of these species, namely, 7. bufo
S. Barkati & M. Ahmed, 1983
Page 33
Figure 2
Thais carinifera: A. dorsolateral view of a portion of an egg mass; B. lateral view of a single egg capsule; C. ventral
view of veliger shell 12 h after hatching; D. dorsal view of the same; E. ventral view of larval shell 36 h after
hatching; F. front view of the same.
Table 2
A comparative account of the characteristics of egg capsules, eggs, and larvae of four species of Thavs.
as averages with the range of values given in parentheses.
Data are presented
Characteristics T. rudolphi T. carinifera T. tissoti T. bufo
Approximate size of females (cm) 6.8 4.6 32 5.8
(4.0-8.0) (3.5-6.0) (2.5-4.0) (4.0-7.0)
Number of egg capsules per mass 170 247 257 80
(97-257) (220-268) (255-295) (65-92)
Capsule height (mm) 4.6 91 4.2 7.9
(3.8-5.0) (8.0-10.5) (4.0-4.4) (7.2-9.0)
Capsule width (mm) 533 13) 1.2 2.0
(4.0-6.1) (1.2-1.5) (1.1-1.2) (1.8-2.5)
Number of eggs per capsule 1094 140 37 228
(813-1422) (120-160) (25-40) (183-268)
Egg diameter (um) 142 230 215 252
(137-148) (216-250) (200-250) (198-350)
Hatching time (days) UF 19 19 20
(16-18) (18-20) (18-20) (18-22)
8220x255
Larval size at hatching (Lx W) (um) 224 x 173 340 X 276 231 x 198
Page 34
The Veliger, Vol. 26, No. 1
Figure 3
Thats tissott: A. dorsolateral view of a portion of an egg mass; B. lateral view of a single egg capsule; C. ventral
view of veliger shell taken out of a capsule; D. ventral view of 24-h veliger shell; E. front view of 84-h veliger
shell; F. front view of larval shell 13 days after hatching.
and 7. carinifera, may commence slightly earlier on the
coast of Mekran than on the coast of Karachi. Be as it
may, spawning in the four species of 7hazs seems to occur
with the rising temperatures of spring and summer when
a lowering of salinity may also occur due to the southwest
monsoon rains (see AHMED, 1980).
The study shows that 7. rudolphi produces the highest
Table 3
Changes in the size of the larval shell of Thais tissott. Egg
size 1s 200-225 um.
Size (um)
Just
after
hatch-
ing 12h 36h 60h 84h 9d
Length 231 281 313 338 385 460
Width 198 229 232 269 302 442
numbers of eggs per capsule, and 7. carinifera, T. bufo,
and 7. tissote follow it in that order. Survival of the brood
in the natural environment seems to be in the same pro-
portion, since 7. rudolphi is the most abundant species of
Thais on the coast of Karachi followed by 7. carinifera.
Thais rudolphi has not been recorded from Gawader and
Jiwani on the Mekran coast where 7. carinifera does occur
(AHMED et al., in press). Thais rudolphi, the species with
the highest fecundity, also has been found in the present
study to have eggs and larvae of the smallest size among
the four species. Larvae of the four species spend about
16-22 days within egg capsules but those of 7. rudolphi
hatch the earliest.
Species of Thais are known to display two types of
larval development. The first is the indirect development
in which pelagic planktotrophic or lecithotrophic veliger
larvae hatch from egg capsules. The second is direct or
non-pelagic development in which crawling miniature
snails emerge from egg capsules and where a planktonic
stage is missing. The four species of 7hais examined in
the present study also possess indirect development, which
S. Barkati & M. Ahmed, 1983
Page 35
Figure 4
Thais bufo: A. lateral view of an egg mass; B. and C. dorsal and ventral views of egg capsules; D. ventral view of
a veliger shell taken out of a capsule just before hatching; E. front view of the same; F. tip of an egg capsule.
is shown by a majority of the species of Thais studied so
far in different parts of the world: for instance, 7. cari-
nifera (THORSON, 1940); 7. fasciata (LEBOUR, 1945); 7.
coronata (KNUDSEN, 1950); 7. bufo, T. tissotz, and three
unidentified species of Thais from India (NATARAJAN,
1957); and 7. haemastoma (D’AsaArRo, 1970). Species that
show direct development are 7. hippocastaneum (THORSON,
1940), 7. lapillus (see THORSON, 1940), 7. lamellosa, T.
emarginata (=T. lima), and T. canaliculata (see AHMED &
SPARKS, 1970), and 7. emarginata (LEBOEUF, 1972; SPIGHT,
1976). There are, however, instances where members of
the same species of 7hais may behave differently under
different environmental conditions. For instance, 7. hae-
mastoma is believed to have pelagic larval development in
Louisiana but direct development in the West Indies (see
THORSON, 1950; NATARAJAN, 1957). Lyons & SPIGHT
(1973) have considered the members of the Muricacea as
sufficiently variable that geographically separated species
may develop according to the local conditions. We wish
to point out here that some workers feel that the above
reference to direct development in the West Indian species
of Thais is based on misinformation and should not be
attributed to either Thorson or Natarajan.
It is generally believed that species of prosobranch mol-
lusks occurring in cold waters of higher latitudes show
direct development but those occurring in warm tropical
and subtropical latitudes possess pelagic indirect devel-
opment (THORSON, 1950). However, MILEIKOvSKyY (1971)
pointed out, as an exception to Thorson’s generalization,
that pelagic development is not altogether absent in colder
waters of higher latitudes and that an occasional species
may display such a developmental pattern. Also as an
exception can be mentioned the case of the gastropod
Planaxis sulcatus which shows direct development on the
coast of Karachi, a subtropical locality (BARKATI &
AHMED, 1982).
LITERATURE CITED
AHMED, M. 1980. The breeding and recruitment of marine
animals of the coast of Pakistan bordering the Arabian Sea.
Proc. First Pakistan Cong. Zool: pp. 55-96.
AHMED, M., H. N. Rizvi & M. MoazzaM. The distribution
and abundance of intertidal organisms on some beaches of
Mekran coast in Pakistan (northern Arabian Sea). Pakistan
J. Zool. (in press).
AHMED, M. & A. K. Sparks. 1970. A note on the chromosome
Page 36
number and interrelationships in the marine gastropod ge-
nus Thais of the United States Pacific coast. Veliger 12:293-
294.
ANNANDALE, N. & S. Kemp. 1916. Fauna of the Chilka Lake.
Mollusca, Gastropoda and Lamellibranchiata with an ac-
count of the anatomy of the common Solen etc. Mem. Ind.
Mus. Calcutta: pp. 328-366.
BARKATI, S. & M. AHMED. 1982. Studies on the reproductive
biology of some prosobranchs from the coast of Karachi
(Pakistan) bordering the northern Arabian Sea. I. Obser-
vations on Planaxis sulcatus (Born, 1780). Veliger 24(4):
355-358.
D’Asaro, C. N. 1970. Egg capsules of prosobranch mollusks
from South Florida and the Bahamas with notes on spawn-
ing in the laboratory. Bull. Mar. Sci. 20:414-440.
Desal, B. N. 1962. A preliminary note on the eggs and larvae
of some marine molluscs of Bombay. Curr. Sci. (Bangalore)
4:158-159.
GanapaTl, P. N. & S. R. Sastry. 1973. The spawn of a
cymatid gastropod, Cymatium pileare. Curr. Sci. (Bangalore)
42(1):25.
Gonar, H. A. F. & A. M. Elsaway. 1962. The egg masses
and development of Trochus erythraeus from the Red Sea.
Publ. Mar. Biol. Sta. Al-Ghardaqa, Egypt, No. 12:191-
203.
Gonar, H. A. F. & A. M. Etsaway. 1967a. The egg masses
and development of four taenioglossan prosobranchs from
the Red Sea. Publ. Mar. Biol. Sta. Al-Ghardaqa, Egypt,
No. 14:109-147.
Gouar, H. A. F. & A. M. ElsAway. 1967b. The egg masses
and development of five rachiglossan prosobranchs. Publ.
Mar. Biol. Sta. Al-Ghardaqa, Egypt, No. 14:215-268.
The Veliger, Vol. 26, No. 1
KASINATHAN, R., K. GOVINDAN & R. NATARAJAN. 1974. Notes
on spawning and hatching of three species of Gastropoda.
Malacol. Rev. 7:133-135.
KNUDSEN, J. 1950. Egg capsules and development of some
marine prosobranchs from tropical west Africa. Atl. Rep. 1:
85-130.
LEBOEUF, R. 1972. Thais emarginata: description of the veliger
and egg capsule. Veliger 14(2):205-211.
Lrespour, M. V. 1945. The eggs and larvae of some proso-
branchs from Bermuda. Proc. Zool. Soc. Lond. 114:462-
489.
MILEIKovsky, S. A. 1971. Types of larval development in
marine bottom invertebrates, their distribution and ecolog-
ical significance: a re-evaluation. Mar. Biol. 10(3):193-213.
Lyons, A. & T. M. SpicHT. 1973. Diversity of feeding mech-
anisms among embryos of Pacific Northwest Thais. Veliger
16:189-194.
NATARAJAN, A. V. 1957. Studies on the egg masses and larval
development of some prosobranchs from the Gulf of Man-
nar and the Palk Bay. Proc. Ind. Acad. Sci., Sect. B. 46:
170-228.
RAMAMOORTHY, K. & R. NATARAJAN. 1973. Spawning in Te-
lescopium telescoprum. Venus 31(4):157-159.
SpiGHT, T. 1976. Hatching size and the distribution of nurse
eggs among prosobranch embryos. Biol. Bull. 150:491-499.
THORSON, G. 1940. Studies on the egg masses and larval de-
velopment of Gastropoda from the Iranian Gulf. Danish
Scientific Investigations in Iran, Part IJ:159-238. Ejner
Munkegaard, Copenhagen.
TuHorson, G. 1950. Reproductive and larval ecology of marine
bottom invertebrates. Biol. Rev. 25:1-45.
The Veliger 26(1):37-46 (July 1, 1983)
THE VELIGER
© CMS, Inc., 1983
Comparison of Northern and Southern Populations
of Epitonium tinctum (Carpenter, 1864)
Onethe California Coast
CAREY RESCH SMITH
Santa Barbara Museum of Natural History, 2559 Puesta Del Sol Road,
Santa Barbara, California 93105
AMY BREYER
Department of Biology, Sonoma State University,
Rohnert Park, California 94928
Abstract. Epitonium tinctum (Carpenter, 1864) was collected for several years from Bodega Head
to the north and from Carpinteria Beach to the south of Point Conception, California. Northern
populations contained longer shells than southern populations. Northern snails became sexually mature
and changed sex at a larger size than southern snails. There were no distinguishable differences in the
weight and width of specimens between northern and southern snails of similar length. Variation in
shell shape (squat versus elongate) between populations did not exceed variation within each population.
Shell length and the number of body whorls overlapped substantially between the two sites. The size
and abundance of snails collected monthly fluctuated more throughout the year in the northern popu-
lation than in the southern population.
INTRODUCTION
ALONG THE WEST coast of North America the wentletrap
Epitonium (=Nitidiscala) tinctum is found intertidally in
association with the aggregate or clonal anemone Antho-
pleura elegantissima (Brandt, 1835). Epitonium tinctum
ranges from Magdalena Bay, Baja California to Forrester
Island, Alaska (DUSHANE, 1979). As protandric her-
maphrodites, the snails mature first as malesyjthen, at a
larger size they change sex and function as females
(BULNHEIM, 1968; BREYER, 1982). Females produce a
number of sand-encrusted egg cases which are strung to-
gether with a strong elastic mucous thread attached to the
substrate or to the shell. When exposed at low tide, snails
bury themselves in the sand between anemones and are
often aggregated around a cluster of egg cases. When sub-
merged during high-tide periods the snails become active
and feed on the expanded tentacles of the anemones
(HocHBERG, 1971; SMITH, 1977; BREYER, 1982). In order
to feed, the snails evert an acrembolic proboscis and either
slip the distal end over a tentacle tip or attach it at some
point along the length of the tentacle. Jaws and radula
are used to sever a portion of the tentacle which is then
ingested upon retraction of the proboscis (RESCH, 1972).
The shell of Epztonium tinctum can grow to over 10 mm
in length. It has three nuclear whorls and up to 8 post-
nuclear whorls with about 12 thin axial costae continuous
from whorl to whorl. STRONG (1941) examined shells from
north and south of Point Conception, California, and not-
ed that northern specimens were longer and appeared to
be heavier and broader than southern individuals. He sug-
gested the subspecific name of swbcoronatum for the north-
ern form. Although DUSHANE (1979) described similar
differences, she did not recognize the subspecies suwbcoro-
natum because radulae from northern and southern snails
were indistinguishable.
Individuals of populations living in food-rich environ-
ments or in warm climates may be expected to grow faster
than those living in more severe environments. This faster
Page 38
128° 126° 124° 122°
—-
DN 42°
* Bodega Head
/
/
( 40°
San 1
Francisco \
St 38°
Point ‘
Conception \
SC
Carpinteria Beach—
Los \
e Angeles
36°
34°
7 A
Figure 1
Map of California showing two study sites located north (Bodega
Head) and south (Carpinteria Beach) of Point Conception.
growth may lead to an altered size at maturity and per-
haps an important difference in generation time. In the
present work we document differences within and be-
tween populations of Epitonium tinctum to the north (Bo-
dega Head) and to the south (Carpinteria Beach) of Point
Conception, California (Figure 1). Providing the major
basis for comparison are shell parameters, which include:
length, width, weight, and number of whorls and costae.
Distinct population modes were computed from measure-
ments of shell length. The mean minimum size at. onset
of sexual maturity and sex change were calculated from
lengths of juveniles, males, and females. Additionally,
fluctuations in size and abundance were noted monthly
from July, 1977, to July, 1979, for populations at Bodega
Head, and from July, 1978, to June, 1980, for popula-
tions at Carpinteria Beach.
MATERIALS ann METHODS
Collection Sites
The northern collecting site was in Horseshoe Cove
located on the exposed outer coast of Bodega Head, So-
The Veliger, Vol) Zo3Noml
25]
BE Bodega Head (n= 1692)
[) Carpinteria Beach (n=840)
no
(eo)
—
= =
fo) a
——_ —
Percent of Total Number of Snails Collected
o
4
1 2 3 4 5 6 7 8 9 ie) 4
Size Class (mm shell length)
Figure 2
Comparison of E. tinctum shell length and the percentage of total
number of snails collected from 1977 to 1980.
noma County, California. In a protected area on the
northern side of the cove, a 3-m-wide surge channel lo-
cated about 10 m from shore is bordered on one side by
a cliff. The channel is parallel to the cliff for about 15 m
until its mouth opens toward the west. Wave disturbance
in this channel is reduced, not only because waves break
to the south, but also because it is protected by an exten-
sive rock shelf. At this site clones of Anthopleura elegan-
tissima cover extensive areas on the sides and bottom of
the channel. In the summer and fall, when wave action is
reduced, the sand between the anemones is fine grained
and at least 10 mm deep. During the winter, when wave
action is heaviest, the amount of fine sand between the
anemones is reduced, disappears altogether, or is replaced
by coarser sand. Snails were collected from the anemone
beds on both sides of the channel.
The rocky reef area at Carpinteria Beach State Park,
Santa Barbara County, California was the southern col-
lecting site. Carpinteria Beach, like much of the southern
California coastline south of Point Conception, is char-
acterized by sandy beaches interrupted by intermittent
rocky outcrops or headlands. The Carpinteria Beach site
consists of a sandy beach extending out from the cliff
about 100 m to where the first rock outcrop begins. In the
mid-intertidal region of the rocky reef both clonal and
solitary Anthopleura elegantissima are present. Epitonium
tinctum is most often found in protected areas on these
rocks in sand which accumulates within pockets between
clonal anemones and beneath the algal cover of Ulva lobata
(Kutzing, 1849) and Gigartina canaliculata (Harvey, 1841).
C. R. Smith & A. Breyer, 1983
Page 39
Bodega Head
Number of Individuals
2 3 4 5
Shell Length (mm)
7 8 9 10 11 12
[] Juvenile
Ao
As
[9
Carpinteria Beach
i 8 9 10 11 12
Figure 3
Comparison of £. tinctum shell length versus the number of juveniles, males, and females in each population. Snails
in transition from male to female (possessing both spermatozeugmata and ova) are also indicated.
Although this area receives gentle surf year around, a
perceptible change occurs in the structure of the beach
between summer and winter. In summer, a sand bar fills
in the area between the shore and the first rock outcrop.
Sand, several centimeters in depth, fills in the crevices
between clonal anemones and covers many of the solitary
anemones, which are primarily located lower in the in-
tertidal. Algae flourish during this time and cover exten-
sive surfaces of rocks. During winter storms much of the
sand cover is removed from between the clonal anemones
and the algal cover on the rocks is reduced.
Methods
Epitonium tinctum was collected approximately month-
ly at low tide from each site; from July, 1977, to June,
1979, at Bodega Head and from July, 1978, to June,
1980, at Carpinteria Beach. Additional collections were
made in 1980 and 1981 at both locations. Snails were
collected by carefully searching among aggregations of
Anthopleura elegantissima in an area approximately 3 m?
for 30 minutes. Similar areas, exposed at mean lower low
water, were used for repeated collections at each site. Snails
were located by visually scanning the area or by lightly
stroking the anemones with fingertips. Pressure on the
anemone body caused the release of a small amount of
fluid which washed over the anemone bed and removed
some sand and debris. When the tip of a snail or a clump
of eggs was spotted it was carefully removed by hand.
Often a mucoid thread was attached from the snail or eggs
being removed to other snails and eggs in an aggregation.
Care was taken to remove all snails and eggs in a partic-
ular aggregation before searching for additional snails.
Lengths and widths of snails were measured using a
variety of dissecting microscopes with calibrated ocular
micrometers. The number of post-nuclear whorls was de-
termined by placing the shell with the operculum facing
upward and counting from the largest body whorl to the
smooth nuclear whorls. Axial costae were counted from
the first costa behind the outer lip, around the body whorl,
994
504
Percent Sexually Mature Individuals
e Bodega Head
x Carpinteria Beach
0.01
1 2 3 4 5 6 7 8 9 10
Size Class (mm shell length)
Figure 4
Mean minimum size of E. tinctum at onset of sexual maturity.
A. Males replaced juvenile snails at an average length of 2.6
mm in Bodega Head and 1.9 mm in Carpinteria Beach. B.
Females replaced males at an average shell length of 7.3 mm in
Bodega Head and 5.4 mm in Carpinteria Beach. No significance
test was run between sets of lines; an appropriate test is not yet
in print (Wenner, in preparation).
to the point where the first costa met the costa directly
above it. Weights (to 0.1 mg) were obtained on a Mettler
balance from animals and shells originally preserved in
50% isopropyl alcohol, which were removed from the al-
cohol and allowed to air dry 24 hours at room temperature
before weighing. ;
To determine sex, snails preserved in 70% ETOH or
50% isopropyl alcohol were first measured and then placed
in a vial filled with Bouin’s solution for 24 hours to dis-
solve their shells. Individuals were then examined with a
dissecting microscope at approximately 50. Males were
recognized by the presence of spermatozeugmata, which
were clearly visible as very white, almost iridescent strands
densely packed in the gonad especially to the right of the
stomach. Females were distinguished by the absence of
spermatozeugmata and the presence of oocytes and ova.
Several snails, termed hermaphroditic, were characterized
The Veliger, Vol. 26, No. 1
by having proximally located spermatozeugmata and dis-
tally located oocytes and ova in their gonads.
Probability Paper Analysis of Polymodal
Frequency Distributions
The technique of plotting cumulative normal distribu-
tions on probability graph paper, first descrbed by Har-
DING (1949), with methodology presented by CAssIE
(1950), is a valuable graphical method with which to ana-
lyze bimodal or polymodal size-frequency distributions in
a population. In a polymodal size-frequency sample, in-
dividual modes may be expanded and the mean and stan-
dard deviation calculated from each mode (see CASSIE,
1954, for method). If modes are compared from two or
more populations, subtle differences may be distinguished.
Probability paper analysis has been utilized to compare
sex ratios and size in crustacean populations (WENNER,
1972) and to define and compare the mean minimum size
at onset of sexual maturity in populations of the sand crab
Emerita analoga (Stimpson, 1857) from different locations
(WENNER et al., 1974).
RESULTS
A compilation of size-frequency data for all snails col-
lected and measured over a two-year period in Bodega
Head and Carpinteria Beach is presented in a histogram
(Figure 2). From these data a polymodal analysis of each
population was calculated by the use of probability graph
paper. That analysis indicated larger snails were more
prevalent at the northern site than at the southern site.
The modes that appear in each population were then ex-
panded, also by the use of probability paper. Three dis-
tinct modes were calculated for each population consisting
of small, medium, and large snails. For Bodega Head
these values were, respectively, as follows: x = 2.20 +
0.55 mm, n= 152; x = 5.40 + 1.20 mm, n= 1134; x=
8.35 + 1.15 mm, n = 406. For Carpinteria Beach values
were, respectively: x = 2.65 + 0.77 mm, n=193; x=
4.75 + 0.90 mm, n = 487; x = 7.20 + 0.90 mm, n = 160.
Since these snails are protandric hermaphrodites, chang-
ing from juveniles to males and then from males to females
as they grow, the modes that appear possibly represent
the juveniles, males, and females in each population.
More than 600 snails were examined for the presence
or absence of spermatozeugmata during spring and fall
(Figure 3). The size at which these protandric hermaph-
rodites became sexually mature and changed sex was
greater in the northern population than in the southern
population. In the transition from male to female in each
population, snails were occasionally found with both sper-
matozeugmata and ova present. The data for transition of
juveniles to males and males to females were plotted on
probability paper (Figure 4) and the mean minimum size
was calculated (e.g., WENNER et al., 1974). The mean size
of females was larger at Bodega Head (7.3 mm) than at
C. R. Smith & A. Breyer, 1983
Page 41
Dh
NO
[o)
———e
=
oa
fi
=
——
Log Snail Weight (mg)
e Bodega Head
x Carpinteria Beach
T aa fo T
1 2 3 4 5
Vier aa ree T
6 7 8 9 10 11
Snail Length (mm)
Figure 5
Comparison of E. tinctum length versus weight. A complete overlap existed between sets of points, so only one
curve was fitted (by inspection).
Carpinteria Beach (5.4 mm). The mean size of juveniles
was also larger at Bodega Head (2.6 mm) than at Car-
pinteria Beach (1.9 mm).
The weights of snails (from 1.7 to 91.3 mg) in each
population were obtained for snails ranging in length from
1.9 to 11.0 mm (Figure 5). The results revealed little
variation in weight of snails at the same length between
populations. The width of snails relative to shell length
from both populations varied somewhat (Figure 6). We
observed that some snails within each population ap-
peared to have either a more squat or more elongate shell
shape than the others. Although the range of variation
within each population was notable, regression lines did
not differ significantly between northern and southern
populations. Snails of similar lengths varied considerably
in number of body whorls (Figure 7), but did not differ
appreciably between populations. The number of axial
costae on the largest body whorl of shells from both lo-
cations ranged between 11 and 14, which agreed with
DUSHANE’s (1979) findings.
The size and abundance (Figure 8) of Epitonium tinc-
tum collected monthly at Bodega Head fluctuated more
than in similar collections from Carpinteria Beach. Small
snails (less than 3 mm) were found occasionally through-
out the year at Bodega Head; however, they were most
common from late winter to early summer. In 1978 many
small snails were found in March and April; in 1979 few
small snails were found until June; in 1980 many small
snails were found in January. Every year during the sum-
mer and early fall, snails were common. In 1978 the mean
shell length increased every month during this period. In
the fall large females (longer than 8 mm) were most com-
mon, and particularly large clusters of egg cases associated
with large aggregations of snails were found (Figure 9A).
In the late fall and early winter the abundance of snails
declined. Snail abundance decreased from December, 1977,
to February, 1978, and from February to May, 1979.
Snails remained rare until an influx of small snails ap-
peared.
No clear annual pattern was shown at Carpinteria
Page 42
ithe Vieligern) Vols Zo Noms
5.5
5.0
4.5
4.0
Shell Width (mm)
KS)
a
2.0
e Bodega Head
x Carpinteria Beach
a a enn ne 7
T T T
a
1 2 3 4 5
6 7 8 9 10 11
Shell Length (mm)
Figure 6
Comparison of E. tinctum length versus width. The slopes of the lines were not significantly different (P > 0.01).
The regression for Bodega Head was y = 0.22 + 0.43x (n = 95) and Carpinteria Beach was y = 0.33 + 0.39x (n=
94).
Beach for size or abundance of snails collected from July,
1978, to June, 1980. The mean snail length (4.5 to 6.0
mm) remained fairly constant through time. Newly settled
snails (less than 3 mm in length) occurred commonly at
all seasons. The largest individuals were observed sporad-
ically throughout the year. Egg masses were recorded in
the field in all collections in equal abundance. Snails with
eggs most commonly occurred as individuals or in small
groups (2-4 individuals) with few egg capsules per egg
mass (less than 50 to about 500). Larger snail groups (10-
15 individuals) and large egg masses (1000-5000 eggs)
occurred without respect to season (Figure 9B). During
the winter of 1981, severe storms washed away large
amounts of sand from Carpinteria beaches. It was difficult
to cross on foot from the cliff to the first rock outcrop,
because of the diminished sand coupled with large waves.
In February, 1981, the population of snails was greatly
reduced. An influx of small snails (mean length 3.5 mm)
was noticed in the spring (April, 1981). A population
fluctuation occurred at Carpinteria Beach that year sim-
ilar to fluctuations observed at the Bodega Head site.
DISCUSSION
Our results support the literature on physiological varia-
tion in intertidal molluscs summarized by NEWELL (1964).
He concluded that northern species generally attain a
larger final size than southern ones. WEYMOUTH et al.
(1931) studied the razor clam Stliqua patula (Dixon, 1789),
and concluded that growth in southern localities was ini-
tially more rapid, but less sustained and hence led to
smaller total lengths. There are several reasons why snails
may grow larger at higher latitudes. Higher latitudes gen-
erally imply a decrease in temperature coupled with an
increase in environmental stresses. CHOW (1975) conclud-
ed that the largest Littorina scutulata (Gould, 1849) had
C. R. Smith & A. Breyer, 1983
Page 43
5
Number of Individuals
5
Number of Post-Nuclear Whorls
>
| Bodega Head
O Carpinteria Beach
1 2 3 4 5
7 8 9 10 11
Shell Length (mm)
Figure 7
Comparison of E. tinctum shell length and number of post-nuclear whorls. Along each line the numbers of
individuals are arranged by collecting locality.
higher tolerances to desiccation, wave shock, and osmotic
stress. Thus, a larger snail may be equipped to survive
the harsher environment of higher latitudes better than a
smaller snail.
Recently Breyer (personal observation) observed that
southern California Epitonium tinctum, collected from
Santa Barbara and raised in the laboratory at the Uni-
versity of California, Santa Barbara, are capable of grow-
ing as large as northern California snails. At present we
do not know why snails in the field in southern California
do not grow as large as those collected in northern Cali-
fornia.
Latitudinal variations in populations of Epitonium tinc-
tum closely resemble those found by FRANK (1975) for the
black turban, Tegula funebralis (A. Adams, 1855). In ad-
dition to finding larger snails in northern latitudes, Frank
found that individuals in northern 7egula populations ma-
ture at a larger size and have irregular recruitment.
ROBERTSON (1981) reported similar size differences be-
tween populations of Epztonium albidum (Orbigny, 1842)
in the British Virgin Islands and Barbados. The largest
Virgin Island males were 8 mm long and females ranged
to 16 mm. The largest Barbados Island males were 6 mm
long while females reached 14 mm although most were
11 mm or less in length.
The northern California population of Epztonium tinc-
tum fluctuated in size and abundance more than the south-
ern California population and had a definite periodicity.
In winter, snail populations declined markedly in the north.
Severe winters are known to cause increased mortality in
intertidal molluscs unless animals can migrate or are pas-
sively washed to deeper waters, or unless they can escape
into crevices to hide (CRISP, 1964). Epitonium tinctum was
difficult to locate among anemones during winter. It was
assumed that most snails were washed off the rocks and
died, but others may have escaped and lived out the winter
in protected areas. Even if adults do survive the winter
months, there is evidence that they may not increase in
size appreciably until the spring. Thais (=Nucella) lapillus
(Linné, 1758) grows little from October to March (Lar-
GEN, 1967), and shell growth in Tegula funebralis ceases
completely from November to February (FRANK, 1975).
The return of spring signifies a period of larval settlement
and the cycle continues. Snails grow during summer and
fall until the onset of winter storms. Southern California,
in contrast to the north, generally has milder winters,
calmer waters, and warmer temperatures. In the southern
area it is common to see all stages in the life cycle of a
snail throughout the year.
In the north, Epztonium tinctum larvae may survive in
Page 44
Bodega Head
=
(o}
a
Snail Length (mm)
The Veliger, Vol. 26, No. 1
JASONDJIFMAMJJASONDJFMAMJJASONDJFMAMJJASONDJFMAMJJA
Carpinteria Beach
=
fo)
Snail Length (mm)
a
B
JASONDJFMAMJJASONDJSFMAMJSJASONDJFMAMJJASONDJFMAMJJA
=
a
(o}
=
fo}
{>}
Number of Snails Collected
a
°
> Bodega Head
Carpinteria
Beach
JASONDJFMAMJJSASONDJFMAMJJSASONDJSFMAMJJASONDJFMAMJJA
1978 1979
1980 1981
Figure 8
Size (including mean and standard deviation) and abundance of snails collected at Bodega Head and Carpinteria
Beach from June, 1977, to July, 1981. A. Bodega Head, size. B. Carpinteria Beach, size. C. Bodega Head and
Carpinteria Beach, abundance.
the plankton from late September until settlement, which
often occurs as late as June. In the south, young snails
and eggs are found throughout the year. Preliminary ob-
servations indicate the larvae of E. tinctum grow consid-
erably before they undergo metamorphosis. Before hatch-
ing, veligers of E. tinctum measure about 70 um in length.
In the laboratory we have kept them alive for more than
two months, at which time they had attained a size of
more than 250 um but had not yet metamorphosed. In the
field the smallest snail observed during more than two
years of study was 1.1 mm; apparently, veligers grow
considerably in the plankton before they settle. DEHNEL
(1955) looked at growth rates of embryos and larvae of
northern and southern gastropod populations. He con-
cluded that the rates of growth of embryos and larvae in
northern gastropod populations are often 2 to 9 times
greater than in southern populations of the same species
at a given temperature.
C. R. Smith & A. Breyer, 1983
Page 45
Figure 9
Comparison of the largest groups of snails and their associated egg masses found in fall 1980 collections. A. Bodega
Head (26 September 1980; SBMNH 33878). B. Carpinteria Beach (23 October 1980; SBMNH 33879).
Once veligers metamorphose, growth in general is faster
in warm than in cold seas, but this does not necessarily
mean the largest species live in warm seas. The largest
snails may be the slow-growing species found in cold water;
and within a species, an individual is likely to grow more
slowly, but become larger and older, at the northern limits
of its distribution (FRANK, 1969). This theory is consistent
with our observations. Larger Epitonium tinctum were
found north of Bodega Bay in Fort Bragg, and the largest
specimens were recorded from Forrester Island, Alaska,
the northern limit of distribution for this species.
ACKNOWLEDGMENTS
The authors would like to thank Drs. Roger Seapy, Jo-
seph Rosewater, Demorest Davenport, Robert Robertson,
James Nybakken, and Diane Perry for critically review-
ing the manuscript, and Laurie Marx for preparing the
text figures. Dr. Adrian Wenner assisted at all stages with
the statistical interpretation. Our special thanks go to Dr.
F. G. Hochberg for his continued support and help
throughout this study.
LITERATURE CITED
BREYER, A. 1982. Observations on the reproduction, feeding
and ecology of the wentletrap Epitonium tinctum (Gastrop-
oda: Mesogastropoda). Master’s thesis, Sonoma State Uni-
versity. 50 pp.
BULNHEIM, H. P. 1968. Atypische Spermatozoenbildung bei
Epitonium tinctum. Ein Beitrag zum Problem des Sperma-
tozoendimorphismus der Prosobranchia. Helgol. Wiss.
Meeresunters. 18:232-252.
Cassie, R. M. 1950. The analysis of polymodal frequency
distributions by the probability paper method. N.Z. Sci.
Rev. 8:89-91.
CassiE, R. M. 1954. Some uses of probability paper in the
analysis of size frequency distributions. Aust. J. Mar. and
Freshwater Res. 5:513-522.
Cuow, V. 1975. The importance of size in the intertidal dis-
tribution of Littorina scutulata. Veliger 18(1):69-78.
Crisp, D. J. 1964. The effects of the severe winter of 1962-
63 on marine life in Britain. J. Anim. Ecol. 33:165-210.
DEHNEL, P. A. 1955. Rates of growth of gastropods as a func-
tion of latitude. Physiol. Zool. 28:115-144.
DuSHANE, H. 1979. The family Epitoniidae in the northeast-
ern Pacific. Veliger 22(2):91-134.
FRANK, P. W. 1969. Growth rates and longevity of some gas-
tropod mollusks on the coral reef at Heron Island. Oecologia
2:232-250.
FRANK, P. W. 1975. Latitudinal variation in the life history
features of the black turban snail Tegula funebralis (Proso-
branchia: Trochidae). Mar. Biol. 31:181-192.
HarDING, J. P. 1949. The use of probability paper for the
graphical analysis of polymodal frequency distributions. J.
Mar. Biol. Assoc. U.K. 28:141-153.
HocuBerG, F. G. 1971. Functional morphology and ultra-
structure of the proboscis complex of Epitonium tinctum
(Gastropoda: Ptenoglossa). ECHO (West. Soc. Malacol.) 4:
22-23.
LarGEN, M. J. 1967. The influence of water temperature
upon the life of the dog-whelk Thais lapillus (Gastropoda:
Prosobranchia). J. Anim. Ecol. 36:207-214.
NEWELL, G. E. 1964. Physiological variation in intertidal mol-
luscs. In: K. M. Wilbur & C. M. Yonge (eds.), Physiology
Page 46
of Mollusca. Vol. 1. Academic Press, New York. pp. 59-
87.
REscH, C. 1972. Chemical recognition of prey in the gastropod
Epitonium tinctum (Carpenter). Master’s thesis, Univ. Cal-
if., Santa Barbara. 61 pp.
ROBERTSON, R. 1981. Protandry with only one sex change in
an Epitonium (Ptenoglossa). Nautilus 95(4):184-186.
SMITH, C. REscH. 1977. Chemical recognition of prey by the
gastropod Epitonium tinctum (Carpenter, 1864). Veliger
19(3):331-340.
SOKAL, R. R. & F. J. ROHLF. 1969. Biometry. W. H. Free-
man, San Francisco. 776 pp.
The Veliger, Vol. 26, No. 1
STRONG, A. M. 1941. Notes on Epitonium (Nitidiscala) tinctum
(Carpenter). Nautilus 55(2):46-47.
WENNER, A. M. 1972. Sex ratio as a function of size in marine
Crustacea. Am. Nat. 106:321-350.
WENNER, A. M., C. FUsARO & A. OATEN. 1974. Size at onset
of sexual maturity and growth rate in crustacean popula-
tions. Can. J. Zool. 52:1095-1106.
WEyYMoOuTH, F. W., H. C. MCMILLAN & W. H. RicH. 1931.
Latitude and relative growth in the razor clam Siliqua pa-
tula. J. Exp. Biol. 8:228-249.
The Veliger 26(1):47-51 (July 1, 1983)
THE VELIGER
© CMS, Inc., 1983
The Reproductive Cycle of the Trochid Gastropod
Oxystele variegata (Anton, 1839)
M. A. P. JOSKA ano G. M. BRANCH
Zoology Department, University of Cape Town, Rondebosch. 7700, South Africa
Abstract.
Oxystele variegata (Anton, 1839) is a trochid gastropod found commonly in the southern
African intertidal region. Monthly samples over a one-year period were examined for gonadal devel-
opment by comparing dry somatic and gonadal tissue weights and histological sections. Mature oocytes
and sperm could be found in monthly samples of the gonads of all animals over 10 mm in size throughout
the year, but based on changes in gonadal weights two spawning peaks were detected—one in February
and a second in September to October. It seems likely that this temperate species is able to spawn
throughout the year but that spawning is intensified during these peak periods.
INTRODUCTION
Oxystele variegata (Anton, 1839) is a trochid gastropod
which occurs commonly in the rocky intertidal zone in
estuaries and along the southern African coast from south-
ern Angola (KENSLEY & PENRITH, 1972) to Durban in
South Africa (Day, 1974). It is one of four species in the
genus Oxystele that are found in the balanoid zone, where
it is very prominent. Because of its abundance O. variegata
must be a major contributor to the energy budget of this
zone. Based on measurements of the metabolic rate of this
species, KING (1974) estimated that the annual population
production was 46.4 kJ-m™~?-yr'. McQualb (1980, 1982a)
has described how the population of O. variegata is zoned
according to size with the largest animals in the upper
balanoid zone and the smallest lower on the shore. No
attempt has yet been made to ascertain the breeding cycle
with any certainty, but McQuarp (1980) hypothesized
from settlement patterns that spawning occurred through-
out the year, with a peak in February and two smaller
peaks in May/June and September/October, 1977.
Monodonta lineata, a related trochid of the northern cool
temperate regions, has been investigated by DEsaI (1966),
who found that this species spawned from May to August
with male and female gonads showing similar cycles.
UNDERWOOD (1972) investigated the breeding cycle of the
British trochids M. lineata, Gibbula umbilicalis, and G.
cineraria. He found that M. lineata and G. umbilicalis
spawned throughout July and August and less in Septem-
ber. However, G. cineraria did not provide clear evidence
of spawning since histological sections of the gonads ap-
peared the same throughout the year.
UNDERWOOD (1974) also found that the trochid Auws-
trocochlea constricta, which occurs on the west and south-
west coast of Australia, did not show any seasonal change
in the appearance or histology of the gonad, and he con-
cluded that this species spawned throughout the year with
a peak in October/November. PAINE (1971), using energy
content as a measure of reproductive state, concluded that
the western North American trochid Tegula funebralis
spawned once a year during the summer.
In this paper a description is given of the breeding cycle
of Oxystele variegata, based on changes in the ratio of
gonadal/somatic dry weight and gonadal histology during
the course of a full year.
MATERIAL ann METHODS
Monthly samples of Oxystele variegata were collected at
random from the upper balanoid zone at Dalebrook on
the Cape Peninsula (47°07’S, 18°27’E) during the period
April, 1980, to March, 1981. The animals were preserved
in a 5% formalin solution until they could be examined.
Fifteen to 20 animals of each sex were dissected each
month. Every shell was measured across the base at the
widest point and the animal was then removed and the
operculum cut off and measured. The gonad was dissected
out of the somatic tissue and both gonadal and somatic
tissue were dried in an oven at 55°C for 24 h. The dry
Page 48
Table 1
Mean monthly shell sizes and opercular diameters of Ox-
ystele variegata sampled for gonadal development.
Opercular
Shell size (mm) diameter (mm)
Month 3 Q é g
April, 1980 14.9 14.8 5.4 5.5)
May 16.4 16.0 6.0 5.8
June 16.0 16.0 5.8 5.6
August 15.5 16.2 5.4 Dod)
September 16.8 16.7 6.0 6.0
October 16.6 16.5 6.0 59)
November 16.8 16.4 5.8 5.8
December 15.6 16.0 6.1 59)
January, 1981 15.6 15.5 5.6 5.8
February 16.5 16.5 5.9 5.9
March 15.3 16.5 5.4 6.0
Annual mean 16.0 16.1 5.8 5.8
weights of the gonad and of the somatic tissue for each
animal were measured.
In addition to the above animals, two to five specimens
of each sex were collected each month and used to obtain
histological sections of the gonads. The gonads of these
preserved specimens were dehydrated in alcohol and
blocked in paraffin wax. Transverse sections were cut
through the center of the gonads at 10 um. The sections
were dehydrated in alcohol and stained with hematoxylin
and eosin.
The male and female gonadal weights were linearly
regressed on somatic tissue weights for each month. The
data obtained from these regressions were used to calcu-
late monthly gonadal indices. These indices were defined
as the ratio of gonadal to somatic weight, expressed as a
percentage for a standard animal of 0.07 g somatic weight
(with an opercular diameter averaging 5.8 mm).
RESULTS
All specimens dissected, ranging from 13.6 mm to 21.6
mm shell width, had mature gonads throughout the sam-
pling period. Individuals of Oxystele variegata less than
10.0 mm shell width lacked gonads and progressively ‘larg-
er gonads could be found in animals with a shell width of
10.0 mm and upwards.
In both males and females of O. variegata the gonads
lie adjacent to and above the digestive gland, extending
into the shell spiral up to the apex. As with most archaeo-
gastropods, trochids release the unfertilized gametes di-
rectly to the surrounding environment where fertilization
occurs (FRETTER & GRAHAM, 1962; DESAI, 1966; PAINE,
1971; UNDERWOOD, 1972; BRANCH, 1974). Oxystele var-
vegata probably conforms to this pattern since we observed
no egg laying or egg masses. The male gonad is a pinkish,
densely constituted tissue. Histological sections showed that
The Veliger, Vol. 26, No. 1
FEMALE
o +A HA .
oe \ ! 60
somatic weight
0.04 gonadal index 0
0.02 20
is \
J A Ss
gonad weight
0.00
A M J
N
OOL xX anssi} 91eWoSs/peUuoy
0.08
Gonadal & Somatic tissue weights (g)
0.06
gonadal index
0.04
0.02
0.00
1980 1981
Figure 1
Gonadal and somatic dry tissue weights (g) of “standard”? Ox-
ystele variegata with an opercular diameter of 5.8 mm and the
gonadal index (expressed as a ratio of gonad : somatic weight X
100) plotted against time (month). (Bars indicate 95% confidence
levels.)
there were ripe spermatozoa present throughout the year.
The ratio of spermatozoa to spermatids and spermatocytes
differed from individual to individual in the same month,
but spermatozoa never constituted less than 50% of the
area of the testis (as determined from grid counts of the
gonadal sections). The female gonad contains a mass of
white or creamy oocytes, each within a clear jelly coat
which is a feature of the trochids (FRETTER & GRAHAM,
1962; Dersal, 1966; DucH, 1969; UNDERWOOD, 1972,
1974; SIMPSON, 1977; WEBBER, 1977; HESLINGA, 1981).
Mature oocytes were present throughout the year and had
an average diameter of 180 wm, not including the jelly
coat. Histological sections showed immature oocytes were
also present throughout the year, but not common from
January to February or from August to September. No
difference existed in mean shell or opercular diameters
between the sexes of the animals sampled (Table 1).
The gonadal indices show strong correlation between
the sexes, both peaking from September to October, 1980,
M. A. P. Joska & G. M. Branch, 1983
Page 49
and in February, 1981, and both dropping in November,
1980, and March, 1981 (Figure 1). Since this gonadal
index can be affected by changes in somatic weight, an
independent assessment of changes in somatic and gonadal
weights was also undertaken. Both gonadal and somatic
weights were linearly regressed on opercular diameter for
each month. These regressions are shown in Table 2. From
these regressions the gonadal and somatic weights of an-
imals with a standard opercular diameter of 5.8 mm could
be calculated for each month. The somatic weights fluc-
tuated about a mean of 0.07 g for each sex. As shown in
Figure 1 the somatic weights of both sexes peaked above
the mean in September and November and dropped below
the mean in April. The gonadal weights of both sexes
reflected the gonadal indices almost completely, thus con-
firming that in spite of slight changes in the somatic weight
the gonadal index is a reliable measure of reproductive
activity.
The number of non-significant correlations between go-
nadal weight and opercular diameter seen in Table 2 in-
dicates a wide “scatter” amongst the population in certain
months, particularly the males. This scatter is due to the
fact that some individuals are sexually mature at a time
when others have just spawned. Again, however, there
was a strong correlation between the sexes for both the
gonadal and somatic tissue weights, and we are confident
that the gonadal index and changes of gonadal weights do
reflect reproductive cycles.
DISCUSSION
It appears that Oxystele variegata, as with some other tro-
chids (UNDERWOOD, 1972, 1974; SIMPSON, 1977) exhibits
continuous gametogenesis once mature. Synchronization
of spawning still remains important since fertilization is
external and, indeed, the male and female gonadal weights
do peak and fall in unison (Figure 1). Oxystele variegata
congregates in large numbers in the upper balanoid zone
at Dalebrook thus also ensuring proximity of the sexes
during spawning. DeEsal (1966), DucH (1969), and
SIMPSON (1977) also found this clustering behavior in tro-
chids.
Despite this, the gonadal tissue weights (relative to
opercular diameter) showed marked variation between in-
dividuals, particularly around the periods of peak spawn-
ing. However, in all samples dissected during other months
there were always some specimens whose gonadal weights
were well above or below the average and these were
considered to be in pre- or postspawn states respectively.
Such variation in the gonadal weights within the popu-
lation probably indicates that there are some individuals
that spawn out of phase with the bulk of the population.
The presence of some spawned individuals in virtually
every month of the year suggests that spawning occurs
year round although peaking twice a year. These varia-
tions in gonadal weight are reflected in the number of
months in which there were non-significant correlations
between gonadal weights and opercular diameter (Table
2), in contrast to the generally high correlations between
somatic tissue weight and opercular diameter. The two
main gonadal peaks indicate spring and late summer
spawnings with the build up to the spring spawning (Sep-
tember to October) being more prolonged. At present we
have no evidence whether these peaks repeat each year.
It is also apparent from the histological sections, which
showed a constant supply of ripe ova and sperm in the
gonads, and from the irregular but continuous settlement
of recruits to the low shore (McQualp, 1982b), that
spawning probably occurs throughout the year, peaking
in the spring and late summer.
The somatic tissue weights of standard-sized animals
of both sexes remained steady at a mean of 0.07 g, except
for April when they declined. This fall in somatic weight
is possibly because during this period there is a recruit-
ment of new individuals to this zone (McQuaIp, 1982b)
and we speculate that increased feeding competition may
strain existing food sources. By May to June the popu-
lation has declined due to mortality and the somatic weight
increases (Figure 1) together with new algal growth in
autumn. In the upper balanoid zone, from where our sam-
ples were taken, there are only two main macroalgae—
Porphyra capensis and Gelidium pristoides. MCQUAID
(1980) found that both these species have varied calorific
values during the year. Porphyra capensis declined in cal-
orific value during autumn whilst G. pristoides had a max-
imum value in autumn. The drop in calorific value of
some of the food available for Oxystele variegata could
affect the somatic weights, but we found that O. variegata
were not commonly seen on macroalgae, and they possibly
mainly feed on microalgae and sporelings rasped from the
substratum. This is also the opinion of McQualp (1982a).
A drop in the number of sporelings has been found during
April in an analysis of monthly colonization carried out
by Joska (in preparation) and this, too, could explain the
lower somatic weight during this month.
In archaeogastropods the larval stage is brief (FRETTER
& GRAHAM, 1962; DEsal, 1966; UNDERWOOD, 1972;
WEBBER, 1977) and settlement on the shore should take
place within a week of spawning. McQualip (1982a, b)
found that 5 to 6-mm specimens of O. variegata were de-
tectable in large numbers in February with a smaller peak
in June/July. In addition, small numbers could be found
throughout the year. Since specimens of O. variegata take
about four months to reach a size of 5 to 6 mm, these
juveniles probably settled about four months earlier, and
are likely to have been the result of, respectively, the spring
and late summer spawnings that we have recorded.
Temperature is a factor often cited as being of great
importance for spawning or reproduction in marine in-
vertebrates. During the period of sampling the sea tem-
peratures rose during the spring spawning but fell at the
time of the late summer spawning (Figure 2). Apart from
suggesting that a minimum temperature exists for spawn-
ing, there is no obvious influence of temperature on the
Page 50 The Veliger, Vol. 26, No. 1
Table 2
Regression coefficients for regressions of gonad weight (y) on operculum diameter (x): y = a) + a,x and coefficients of
determination (r’) with the probability that r? is significant (P).
Month ao a, ie P
g April, 1980 —0.0155 0.0382 0.2729 0.05
May —0.0340 0.0794 0.4638 0.001
June —0.0152 0.0436 0.2915 0.05
August 0.0194 —0.0046 0.0026 Not significant
September —0.0290 0.1103 0.2988 0.01
October —0.0034 0.0630 0.0232 Not significant
November —0.0252 0.0672 0.3400 0.01
December —0.0093 0.0399 0.2495 0.05
January, 1981 0.0058 0.0251 0.0214 Not significant
February —0.0676 0.1691 0.5365 0.001
March : —0.0281 0.0666 0.5426 0.001
) April, 1980 —0.0222 0.0531 0.1509 Not significant
May : 0.0374 - =0,0317/ 0.0228 Not significant
June —0.0661 0.1363 0.5817 0.001
August —0.0017 0.0439 0.1618 Not significant
September —0.0310 0.1093 0.1910 0.05
October —0.0195 0.0870 0.1710 0.05
November —0.0152 0.0535 0.4046 0.01
December 0.0020 0.0231 0.1047 Not significant
January, 1981 —0.0239 0.0707 0.1925 0.05
February —0.0820 0.1823 0.6314 0.01
March —0.0156 0.0433 0.0940 Not significant
Regression coefficients for regressions of somatic tissue weight (y) on operculum diameter (x): y = a, + a,x and
coefficients of determination (r?) with the probability that r* is significant (P).
Month Aly ay r? P
g April, 1980 0.0346 0.0317 0.9934 0.001
May —0.1638 0.4054 0.8411 0.001
June —0.0601 0.2269 0.4540 0.01
August 0.0622 0.0144 0.0049 Not significant
September —0.0863 0.2825 0.7607 0.001
October —0.1844 0.4410 0.7384 0.001
November —0.0926 0.2923 0.5173 0.001
December —0.0940 0.2788 0.4958 0.001
January, 1981 —0.1105 0.3049 0.7235 0.001
February —0.1199 0.3335 0.5736 0.001
March : —0.1688 0.4166 0.8663 0.001
) April, 1980 —0.0229 0.1282 0.4085 0.01
May —0.0199 0.1610 0.2331 0.05
June —0.1480 0.3823 0.5455 0.001
August 0.0370 0.0659 0.1417 Not significant
September —0.1046 0.3129 0.6867 0.001
October =O1B27 © 0.3571 0.8634 0.001
November —0.0941 0.2979 0.6955 0.001
December —0.0296 0.1709 0.5703 0.001
January, 1981 —0.0758 0.2295 0.6760 0.001
February —0.1319 0.3389 0.8117 0.001
March 0) UZS7/ 0.3222 0.5280 0,001
M.A. P. Joska & G. M. Branch, 1983
Page 51
24
om
O
—
¢
5 20
—
0
hh
o
a
— 16
o
~~
0
o
YM 12
= 1980 1981
Figure 2
Mean monthly sea temperatures during the sampling period.
Bars indicate maximum and minimum temperatures. (Temper-
ature records kindly supplied by the Department of Maritime
Defence, Simonstown.)
reproductive cycle in this species. Dalebrook lies in False
Bay, which because of its shallow waters and current pat-
terns affords year round moderate conditions and pre-
dictable seasonal changes in temperature. Rather more
variant conditions on the west coast could possibly pro-
duce different spawning peaks.
ACKNOWLEDGMENTS
We would like to thank Dr. John Pearse for his pains-
taking criticism of an earlier manuscript of this paper.
The research was supported by a grant from the South
African Committee for Oceanographic Research.
LITERATURE CITED
BRANCH, G. M. 1974. Ecology of Patella Linnaeus from the
Cape Peninsula, South Africa. 2. Reproductive cycles. Trans.
R. Soc. S. Afr. 41(2):111-160.
Day, J. H. 1974. A guide to marine life on South African
shores. A. A. Balkema, Cape Town. 300 pp.
Desai, B. N. 1966. The biology of Monodonta lineata (Da
Costa) Proc. Malac. Soc. Lond. 37:1-17.
Ducu, T. M. 1969. Spawning and development in the trochid
gastropod ELuchelus gemmatus (Gould, 1841) in the Hawai-
ian Islands. Veliger 11(4):415-417.
FRETTER, V. & A. GRAHAM. 1962. British prosobranch mol-
luscs. Ray Society, London. 755 pp.
HEsLINGA, G. A. 1981. Larval development, settlement and
metamorphosis of the tropical gastropod Trochus niloticus.
Malacologia 20(2):349-357.
KENSLEY, B. & M.-L. PENRITH. 1972. Monodonta (Oxystele)
fulgurata Philippi, a synonym of Oxystele variegata (Anton).
J. Conchol. 27:349-352.
KING, J. M. 1974. Population respiration of Oxystele variegata
(Gastropoda). Zoology Honours Project, University of Cape
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McQuaip, C. D. 1980. Spatial and temporal variations in
rocky intertidal communities. Doctoral thesis, Zoology, Uni-
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McQuaip, C.D. 1982a. The influence of desiccation and pre-
dation on vertical size gradients in populations of the gas-
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McQuaip, C. D. 1982b. Population dynamics and growth of
the gastropod Oxystele variegata (Anton) on an exposed rocky
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PAINE, R. T. 1971. Energy flow in a natural population of the
herbivorous gastropod Jegula funebralis. Limnol. Oceanogr.
16(1):86-98.
SIMPSON, R. D. 1977. The reproduction of some littoral mol-
luscs from Macquarie Island (Sub-Antarctic). Mar. Biol.
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UNDERWOOD, A. J. 1972. Observations on the reproductive
cycles of Monodonta lineata, Gibbula umbilicalis and G. cine-
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UNDERWOOD, A. J. 1974. The reproductive cycles and geo-
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The Veliger 26(1):52-61 (July 1, 1983)
THE VELIGER
© CMS, Inc., 1983
The Larval Biology of Brachidontes modiolus
(Linné, 1767) (Bivalvia: Mytilidae)
ANGELA FIELDS anp EUNA MOORE
Department of Biology, University of the West Indies, Cave Hill, Barbados
Abstract. Larvae of Brachidontes modiolus were reared in the laboratory from eggs through to settled
juveniles. Egg sizes ranged between 67.3 and 77 um. Straight-hinge veligers appeared 15 to 17 h after
fertilization of the eggs. The length of shelled larvae increased from 96 to 221 um: the straight-hinge
stage from 96 to 176 um, the umbo stage from 168 to 221 um, and the pediveliger stage from 180 to 221
um. Settlement occurred at lengths of 180 um and upwards. The larval hinge consists of small teeth
along the length of the hinge with larger teeth at both ends. Larvae of B. modiolus develop more rapidly
and settle at an earlier age than larvae of B. recurvus and B. granulata.
INTRODUCTION
Brachidontes modiolus (Linné, 1767) (=B. citrinus) is a
small marine mytilid, the adults of which measure be-
tween 38 mm (ABBOTT, 1974) and 46 mm (MCLEAN,
1951). The geographic range for this species is from Flor-
ida to the West Indies (ABBOTT, 1974). In Barbados,
members of this sublittoral species may be found recessed
within beds of the seagrass Thalassia testudinum Konig or
attached to the rocky surface of reef flats at depths of O-
2 m. Brachidontes modiolus is highly gregarious and,
whether living epifaunally or infaunally, occurs in dense
aggregates of individuals.
The specific name Brachidontes citrinus (Réding, 1798)
has been widely used. ABBOTT (1974), however, consid-
ered this to be a synonym of B. modiolus (Linné, 1767).
Indeed the name ‘modiolus’ is singularly apt, for B. mo-
diolus exhibits characteristics of the Modiolus group of
mytilids, namely the possession of subterminal umbones
and a shell shape which is more conical than triangular
(STANLEY, 1970, 1972).
The larval biology of Brachidontes modtolus has hitherto
been unreported in the literature under any of its syn-
onyms. A knowledge of the duration of the planktonic
stage of an aquatic larva, the time during which it is
exposed to ocean or coastal currents, could contribute to
an understanding of the distribution of a species in a given
region. This aspect has been discussed by COE (1953) and
SCHELTEMA (1971). In addition, a description of the larval
stages of B. modiolus would aid in the identification of
these larvae when encountered in plankton samples, as
well as establish the life history pattern and strategy of
the species.
The identification of bivalve larvae has posed problems
in the past. LOOSANOFF et al. (1966) drew attention to the
inadequacy of “indirect methods” of identification of bi-
valve larvae, and pointed out that these methods have led
to discrepancies in the description of larvae of the same
species when reported by different authors. Indirect meth-
ods include monitoring the development of an unidentified
larva found in the plankton through to settling and the
assumption of identifiable features of a particular species.
These authors recommend “direct methods” of identifi-
cation, 1.e., the rearing of larvae from fertilized egg stage
through to metamorphosis under controlled laboratory
conditions. The development of reliable methods for ob-
taining viable gametes and for the rearing of juveniles has
resulted in the successful culture of the larvae of several
marine bivalves. LOOSANOFF & Davis (1963) reviewed
methods for the cultivation of larvae and detailed the spe-
cific requirements necessary for the successful culture of
19 species of bivalves. As characters to be used in the
identification of marine bivalve larvae, LOOSANOFF e¢ al.
(1966) listed the dimensions of the larval shell (the pro-
dissoconch), its general shape, prominence of the umbones
during growth to metamorphosis, and ratios of length of
hinge to maximum length or width of shell. CHANLEY &
ANDREWS (1971) and CHANLEY & CHANLEY (1980) pro-
vided useful terminology for describing larval shell form
and, in order to provide a better description of larval shell
length, height and depth relationships. LOOSANOFF et al.
(1966) provided a guide to the dimensions and shapes of
A. Fields & E. Moore, 1983
Page 53
20 species of bivalves, and CHANLEY (1970) gave a review
of the larval characteristics of the Mytilidae. Within the
genus Brachidontes, descriptions of the larvae of B. recur-
vus from the western North Atlantic Ocean have been
published in CHANLEY (1970), and of B. granulata from
central Chile in CAMPos & RAMORINO (1980). The lar-
vae of B. senhausi were described in YOSHIDA (1937), but
according to KURODA ef al. (1971; cited in CAMPos &
RAMORINO, 1980), this species belongs to the genus Mus-
culus.
The purpose of this paper is to provide a description of
the larval stages of Brachidontes modiolus, with informa-
tion on the development and length of the larval life of
the species.
MATERIALS anp METHODS
Gametes were obtained from ripe mussels collected during
the peak of the reproductive season (June to September).
This peak was determined by continuous sampling and
histological techniques over a period of two years. In the
laboratory the animals were cleaned of sediment and en-
crustations and placed in freshly collected sea water. Ini-
tially, several methods were employed in an attempt to
obtain viable gametes:
(1) temperature shock within the range 24—34°C;
(2) pricking of the posterior adductor muscles of the adults;
(3) introduction of sperm and/or eggs obtained from
stripped gonads to water containing ripe mussels;
(4) treatment of stripped gonads with a 0.1 N solution of
ammonium hydroxide;
(5) exposing the mussels to hydrogen peroxide in alkaline
(pH 9.1) sea water as per Morsk et al. (1977). Only
this last method was successful; hence, the procedure
is detailed below.
Alkaline sea water was prepared with predetermined
quantities of Trizma*, hydrochloric acid and natural sea
water (pH 7.2). Three or four mussels were placed in-
dividually or collectively in beakers containing 50 ml of
alkaline sea water per animal (pH 9.1); hydrogen per-
oxide was then added with a micropipette to a final con-
centration of 5mM. This was the treatment solution. The
animals were kept in this solution for one hour, after
which time the liquid was decanted and replaced with
100 ml of fresh treatment solution. One hour after the
second treatment, the mussels were removed from the al-
kaline sea water, rinsed, and placed in beakers containing
100 ml of natural sea water. These were then placed in
a water bath at a temperature of 33-34°C. Males and
females received the same treatment. The onset time of
spawning varied widely, from 30 minutes to several hours
after treatment in the hydrogen peroxide solution. Mus-
* A brand name. Use here does not necessarily imply endorse-
ment of the product.
sels seen spawning were removed and placed individually
in beakers containing natural sea water at 28°C. The eggs
were rinsed thoroughly with sea water filtered through
glass fiber filter paper. Sperm was added to the egg sus-
pension, and the two allowed to remain undisturbed for
10 min to encourage fertilization. In some instances a
female in the process of spawning was placed in a weak
sperm suspension, and so the eggs were fertilized as they
were extruded. The fertilized eggs were rinsed to remove
excess sperm and placed in 150 ml of filtered sea water
in Erlenmeyer flasks of 250 ml capacity. Possible contam-
ination of the cultures was reduced by placing tissue paper
in the necks of the flasks and covering the opening of the
flask with aluminum foil. If flasks containing larvae were
left open to the air, a dense population of ciliates soon
developed, with consequent death of the larvae. The em-
bryos were left undisturbed for 24 h, at which time the
strongly swimming larvae were pipetted off and intro-
duced into fresh sea water to a density of 25-30 larvae/
ml. The water containing the larvae thereafter was changed
every third day. This was achieved by washing the larvae
over a fine nylon mesh which was glued securely over one
end of a large open-ended glass tube. Mortality of the
larvae during washing was reduced if the mesh was held
in a beaker containing filtered sea water, so that the mesh
was positioned below the surface of the water. ‘The bottom
layer of water in the flask was discarded as dead or weak
larvae accumulated there. The flasks were thoroughly
washed at each water change, and care was taken to en-
sure that no detergents contaminated the sea water. The
sea water used for each change was freshly collected and
filtered. Best survival rates were obtained when the larvae
were reared in unaerated sea water.
The larvae remained unfed for 48 h and thereafter were
fed on a mixture of Dunaliella tertiolecta and Nephroselmis
tibron. When possible, /sochrysis galbana was added to the
diet. Feeding densities in the case of the larger alga, z.e.,
Dunaliella, was approximately 8000-10,000 cells per ml
of culture solution. Concentrations of the smaller alga were
higher, 70,000-80,000 per ml of culture solution. Algal
concentrations of these magnitudes were cleared by the
larvae in 24 h.
Sub-samples of approximately 10 larvae were mea-
sured every two days for two weeks. Length was measured
as the maximum distance in the antero-posterior direction,
height as the maximum distance from the hinge to the
ventral margin of the shell, and depth as the maximum
left-right dimension (CHANLEY, 1970).
RESULTS
The eggs of Brachidontes modiolus ranged in diameter from
67.3-77 wm, and were a uniform dark brown in color.
When spawned, the eggs had an irregular appearance but
soon became rounded. No measurements were made of
the spermatozoa. The sperm obtained from stripped go-
Page 54 The Veliger, Vol. 26, No. 1
A. Fields & E. Moore, 1983
Page 55
nads appeared less active than those obtained through the
mediation of hydrogen peroxide.
As in BAYNE (1965), the stages chosen to evaluate de-
velopment times to the straight-hinge stage were those
easily recognized and not those with particular embryo-
logical significance (Table 1).
Stage 1—First division: the time at which 50% of the sam-
ple had undergone first cleavage.
Stage 2—The ciliated blastula: first appearance of cilia,
evidenced by slowly rotating larvae (Figure 1a).
Stage 3—The early trochophore: appearance of an apical
flagellum (Figure 1b).
Stage 4—Veliger: appearance of long cilia on the apical
plate (Figure Ic).
Stage 5—Transitional stage: first appearance of the shell
as a transparent object on the dorsal surface of the larva
(Figure 1d).
Stage 6—Straight-hinge veliger: the possession of a com-
plete shell, the prodissoconch. Very early straight-hinge
veligers are darker than the later ones (Figure le).
First division occurred approximately 36 min after fer-
tilization and the ciliated blastula appeared 3 h later. The
ciliated blastulae swam slowly at first and as time pro-
gressed swam upwards towards the surface of the water
column. Development of the trochophore occurred 5 h
after fertilization, and veligers were first seen 4 h later.
Transitional stages between the veliger and the straight-
hinge veliger appeared 12 h from zero time, and straight-
hinge veligers were seen in cultures 15-17 h after fertil-
ization. The color of the larvae underwent a change
during development, and stages 1 through 5 were dark
brown while stage 6, the straight-hinge veliger, was a pale
yellow-brown.
The rate of development of the larvae varied with tem-
perature. Larvae reared at 34°C developed into straight-
hinge veligers 13 h after fertilization. In cultures kept at
24°C, it was not until 25 h had elapsed that straight-hinge
veligers were observed. At the time that straight-hinge
veligers were recorded from cultures reared at 28°, 32°
and 34°C (7.e., between 13-17 h), larvae reared at 24°C
were still at the early trochophore stage.
Larval Dimensions and Shape
The early straight-hinge larvae measure 96 um in length,
with a minimum height of 67 wm. No measurement of
depth was recorded at the earliest straight-hinge stage.
The smallest depth recorded was 56 um at a larval length
Table 1
Summary of the observed development times of the larvae
of Brachidontes modiolus. Temperature = 28°C.
Stage Description Time
0 Fertilization 0
1 First division 34-36 min
2 Ciliated blastula 3h 40 min
3 Early trochophore 5 h 15 min
4 Veliger 9h 15 min
5 Transitional stage 12h
6 Straight-hinge veliger 15-17 h
of 152 wm. Straight-hinge larvae attained a size of up to
176 um in 6 days. Heights then ranged from 126-144 um,
and depths from 84-104 wm. At lengths greater than 176
um the hinge line invariably showed signs of rounding
(Figure 2). Lengths increased faster than height, which
in turn increased faster than depth. Between lengths of
96 and 115 wm, heights were 19-29 um less than length,
while at a length of 176 um, heights measured 32-50 um
less than length. The first indication of umbo development
appeared at 168 wm, with heights ranging from 120-136
um and depths from 72-88 um. All observed combinations
of larval heights and depths for a given length are given
in Figure 3. The length of the hinge at a shell length of
152 um was 120 um, increasing to 128 um at a shell length
of 168 wm. The results are summarized in Table 2 and
Figure 2.
The straight-hinge larva is roughly ““D” shaped. The
hinge line is long relative to the length of the shell. The
shoulders slope steeply, with the posterior shoulder short-
er and sloping more steeply than the anterior. The pos-
terior end is higher and more pointed than the anterior.
The ventral margin of the shell is rounded. The hinge
line becomes slightly rounded with the development of the
umbo, and is at first “round” or “indistinct.”” The umbo
may remain low and not clearly defined through lengths
of 168-288 wm, becoming “broadly rounded” in later
stages. The minimum length at which the umbo was seen
to project above the shell margin is 240 wm. The shoulders
at this stage are almost straight, the anterior shoulder not
sloping as steeply as the posterior. The ventral margin is
now markedly elongate, but still rounded. The larval hinge
consists of a series of small teeth, fanked by two or three
larger teeth.
Figure 1
Stages in the early larval development of Brachidontes modiolus. A. ciliated blastula; B. early trochophore; C. veliger;
D. transitional stage; E. straight-hinge stage.
Page 56
A B
120 x82
E
191 « 146
I
224 x 184
150 x 109
208 x 176
ithe Veligers Volk ZomNomi
Cc D
159x118 173 x 137
218 x 182
J
282 « 264
Figure 2
The larvae of Brachidontes modiolus at different stages of development from the early straight-hinge stage (A) to
settlement (G-I). Larvae are positioned with anterior end to the left, except in J. The larva in J is an early juvenile
just beginning dissoconch growth. The length and height of the larvae are indicated under each photograph;
measurements are in microns.
The smallest pediveliger larva seen using its foot mea-
sured 180 wm (Figure 4) in length, but more generally,
ambulatory pediveligers appeared at a length of 184 um.
The eye spot first appeared in larvae at length 184 um
when cultured at temperatures of 32° and 34°C.
Internal Anatomy of the Larvae
The internal anatomy of the larva was at first indistinct
at magnifications of up to 500X. The gut became apparent
on the first day as a straight tube running in a posterior
direction. It soon became coiled (Figure 5a). The digestive
gland soon became easily visible, as with the onset of feed-
ing in the larvae, the organ developed a green-brown color
(Figure 5b). The adductor muscles showed clearly by the
third day, and the velar retractor muscles were also con-
spicuous at this time. The foot was fully developed by day
6, with the pedal retractor muscles clearly visible (Figure
5c, d). The velum increased in size with the development
of the larva to the pediveliger stage, and occupied a large
portion of the shell cavity. The gill filaments were not
clearly visible until after metamorphosis (Figure 5e). The
A. Fields & E. Moore, 1983
Rage y),
Figure 3
Larval dimensions of Brachidontes modiolus. The height and depth co-ordinates run parallel to the length axis. The
dots represent length-depth or length-height measurements. The lines enclosing the dots were fitted by eye and
represent maximum and minimum height and depth measurements. The three-dimensional figure represents all
possible length, height, and depth combinations for B. modiolus (after CHANLEY & VAN ENGEL, 1969). The clear
area represents the straight-hinge stage, the lined area the umbo stages, and the stippled area, the transitional stage
between straight-hinge and umbo forms.
larvae of Brachidontes modvolus settled at sizes between
180 and 221 um in length and settlement occurred from
day 11 onward, although swimming larvae were still vis-
ible in the medium up to the 30th day.
DISCUSSION
Induction of Spawning
LOOSANOFF & Davis (1963) list methods used in the
induction of spawning in 19 bivalves. They pointed out
that where some species responded to thermofluctuation
as a stimulus to spawning, others needed the additional
stimulus of a sperm or egg suspension. In some instances
special methods had to be employed, such as pricking the
Table 2
Summary of larval dimensions of Brachidontes modiolus.
Length Height Depth
Stage (um) (um) (um)
Early straight-hinge stage 96 76 2
Straight-hinge stage 96-176 67-152 *_100
First indication of umbo 168 120-136 72-88
Umbo stage 168-221 120-184 72-124
* Not measured.
Page 58
The Veliger, Vol. 26, No. 1
Figure 4
Pediveliger of Brachidontes modiolus.
adductor muscle in Mytilus edulis. Other species, like
Modiolus demissus, did not respond to any treatment;
LOOSANOFF & Davis (1963) were unsuccessful in induc-
ing this species to spawn. WILSON & HODGKIN (1967)
failed to induce spawning of Brachidontes cf. variabilis in
the laboratory. CHANLEY (1970) was finally successful in
causing spawning in B. recurvus by placing the mussels
in sea water with temperatures fluctuating between 20
and 32°C. Previous attempts to induce spawning in this
animal, by adding stripped gametes to the water or
stretching or injuring the adductor muscles, had proved
unsuccessful. Ripe adults of B. granulata spawned when
placed in filtered sea water at 16°C after being held in an
incubator at 6°C for 12 h. The account presented above
demonstrates the individuality of the response of different
species to various spawning stimuli.
Stripping of the gonad of Brachidontes modiolus failed
to produce viable gametes for the same reason that the
eggs obtained through the mediation of 0.5 M KCl are
not fertilizable. RAVEN (1958) stated that maturation of
the eggs of most mollusks may begin spontaneously, in-
dependent of fertilization, e.g., after spawning in sea water,
and continues until metaphase of the first maturation di-
vision. Unfertilized eggs are blocked at this stage. Matu-
ration is evidenced in part by the dissolution of the ger-
minal vesicle. The ova of B. modiolus are not mature while
still in the gonad. Eggs from this species, when obtained
by stripping or by injection of KCl, possessed an intact
germinal vesicle and were therefore immature and were
incapable of being fertilized without further treatment (e.g.,
the addition of NH,OH). In contrast, the eggs extruded
from mussels stimulated by the addition of hydrogen per-
oxide had started the maturation process and were easily
fertilizable.
Mors et al. (1977) found that the hydrogen peroxide-
induced spawning of the abalone Haliotis rufescens may
have resulted from a “direct activation of the enzyme-
catalyzed synthesis of prostaglandin endoperoxide.” Pros-
taglandin endoperoxide (PGEP) is produced from arachi-
donic acid through a series of reactions, the first step of
which is catalyzed by the enzyme fatty acid cyclooxygen-
ase (=PGEP synthetase). These investigators showed that
abalone eggs and gonads from ripe animals of both sexes
contained large quantities of cyclooxygenase, and further
that hydrogen peroxide directly increased the rate of the
reaction catalyzed by the PGEP-forming cyclooxygenase
from reproductive cells of the abalone. PGEP synthetase
has been implicated in the control of spawning not only
in abalones, but in Mytilus californianus (MORSE et al.,
1977) and sea urchins (MorsE et al., 1978). It is probable
that a similar control of spawning exists in Brachidontes
modiolus. IWATA (1952) found that electrical stimulation
induced maturation of eggs of Mytzlus edulis. He suggested
that the stimulus was mediated by the ovary, probably by
the secretion of some substance that caused the ova to
mature. According to IWATA (1952), spawning in Mytilus
appeared to follow automatically as soon as the eggs begin
the maturation division, and therefore spawning in this
animal depended entirely on whether the maturation pro-
cess had taken place. A number of questions arise from a
comparison of the results of MorsE et al. (1977) and Iwa-
TA (1952). Could the proposed substance of Iwata (1952)
be related to PGEP synthetase, or to any of the enzymes
or intermediate products of PGEP production? Converse-
ly, does PGEP synthetase act to promote maturation of
oocytes and hence spawning?
The role of PGEP synthetase in the control of spawning
in Brachidontes modiolus would be of interest for further
study. Morse et al. (1977) stated that the fatty acid-cy-
clooxygenase reaction may be potentially rate-limiting in
the physiological sequence of reactions leading to spawn-
ing and therefore possibly under hormonal and/or neural
control. Thus a knowledge of the levels of this enzyme in
B. modiolus, together with information on environmental
factors, could help in determining the ultimate factors con-
trolling the release of gametes in this species.
Larval Survival and Development
Larvae survived well in unaerated cultures, and change
of water every third day proved adequate for removing
toxic waste products before harmful levels were reached.
Some morphological malformations were observed in some
of the larvae, for example concavity of the hinge line or
un-equal valve growth; but it could not be determined to
what extent these were due to culture conditions. Abnor-
mality of the hinge line as seen in Brachidontes modiolus
was also reported for other bivalves (LOOSANOFF & DAVIS,
1963). In addition, these authors described another type
A. Fields & E. Moore, 1983
Page 59
PAM
AAM
Figure 5
Diagrams of conspicuous features of the internal anatomy of Brachidontes modtolus. a. straight-hinge veliger; b. 3-
day old larva; c and d. 6-day old larvae; e. spat. Scale bar for a, b, c, and d is 40 um long; for e, it is 60 wm long.
AAM, anterior adductor muscle; DG, digestive gland; ES, eye spot; F, foot; Gi, gills; I, intestine; PAM, posterior
adductor muscle; PRM, pedal retractor muscle; St, stomach; U, umbo; V, velum.
of larval abnormality in which there was no clear-cut
anatomical malformation, but rather the larvae were un-
able to feed. Such larvae developed to the straight-hinge
stage but grew no further and eventually died. It is prob-
able that the larvae found in the bottom layers of cultures
of B. modiolus suffered from this type of “feeding” abnor-
mality. LOOSANOFF & Davis (1963) reported that this
type of abnormality in Mercenaria mercenaria was related
in some instances to the type of food fed to the larvae.
This aspect was not investigated in B. modiolus.
That larvae of various species of bivalves show variation
in growth rate among individuals reared from the same
spawn under similar conditions is well established
(LOOSANOFF & Davis, 1963). In addition to individual
variation in growth rate, larvae of Brachidontes modiolus
settle at different times after 11 days. LOOSANOFF & Davis
Page 60
Whe Veliger, Vol] 2Z6@Noml
Table 3
Summary of the major features of the larvae of Brachi-
dontes modiolus, B. recurvus*, and B. granulata**.
Size (um)
Stage or B. B. B.
distinctive feature modiolus recurvus granulata
67-77 62-68 63-73
Unfertilized egg
Straight-hinge veliger 96-176 90-165 177+
Appearance of umbo 168 135 150
Conspicuous eye spot 184 180 —
Pediveliger (first appearance
of functional foot) 180 165 200
* Data taken from CHANLEY (1970).
** Data taken from CAMPOS & RAMORINO (1980).
+ Length of prodissoconch.
(1963) found that the number of days needed for larvae
of the same cultures to reach settling stage was not sharply
defined, even for a culture reared under standard well-
controlled conditions. The observed extended settling pe-
riod of B. modiolus may be explained by the probability
that glass is not the most desirable substrate for settling,
as well as it may be related to factors governing settling
density. Larvae possessing a functional velum could be
seen swimming in the water column long after others in
the same flask had settled and attached themselves by
byssal threads. BAYNE (1965) discussed the delay of meta-
morphosis in Mytilus edulis and showed that the larvae
become capable of attachment and metamorphosis some
time before they would attach to glass, and that the ma-
jority died without attachment. The delay of metamor-
phosis of laboratory reared larvae has been previously
reported for other bivalves: CULLINEY (1971) for Lithoph-
aga bisulcata, CAMPOS & RAMORINO (1980) for Brachi-
dontes granulata. BAYNE (1965) established that the larvae
of Mytilus edulis settled preferentially on filamentous al-
gae (primary settlement). The larvae of B. modiolus did
not settle on algae provided in the culture flasks. However,
in another experiment not described here, a fine filament
of artificial fiber of unknown origin precipitated mass gre-
garious settlement of larvae of B. modiolus. In the wild
population no sign of attachment to algae by the larvae of
B. modiolus was recorded in this study. ;
CHANLEY (1970) described the common characteristics
of larval Mytilidae. The larvae of Brachidontes modiolus
exhibited many of the features listed. The hinge line was
long in relation to larval length and increased in size with
growth of the larvae. The hinge possessed a mytilid den-
tition, having a series of small teeth along the length of
the hinge, with larger teeth towards the end. The umbo
was late in developing and remained indistinct. In fact, it
was not until after settling that the umbo of B. modiolus
became pronounced. However, the larvae of B. modiolus
set at a smaller size (180-221 um) than most mytilid
larvae (300 um, in CHANLEY, 1970) as do larvae of other
species of this genus (Table 3).
A comparison of the development of the larvae of
Brachidontes modiolus, B. recurvus, and B. granulata (Ta-
ble 3) reveals differences in size at first appearance of the
umbo and in minimum sizes of the pediveligers. The shape
of the straight-hinge veliger of B. modiolus more closely
resembles that of B. recurvus than that of B. granulata.
The shape of this larval stage of B. granulata is more
rounded than that of the former two. If, however, a com-
parison is made of later stages, the position is reversed,
with the larvae of B. granulata being more similar in shape
to that of B. modiolus than B. recurvus. The most notable
difference is in the developmental times of the three species.
Pediveligers first appeared after 6 days and settlement of
the larvae of B. modiolus occurred from the 11th day on-
wards, similar to the time of the first appearance of ped-
iveligers of B. recurvus. CHANLEY (1970) does not report
on the time of settlement of B. recurvus. The pediveligers
of B. granulata do not appear until 55 days after fertiliza-
tion, and CAMPOS & RAMORINO (1980) report no evidence
of metamorphosis up to 33 days after this. This lack of
metamorphosis in the larvae of B. granulata was attributed
to the unavailability of a substrate suitable for settlement
of the pediveligers. The variation in the developmental
times may result from the different temperature regimes
to which the larvae were exposed. The larvae of B. granu-
lata were reared at 12-16°C, those of B. recurvus at 25°C,
and the larvae of B. modiolus at 28°C. BAYNE (1976) pre-
sented data from various authors on the rates of cleavage
and early development of Mytilus edulis at different tem-
peratures (8-22°C). Those results showed that develop-
ment proceeded more rapidly at the higher temperatures.
In general the developmental progress and morphology
of the larvae of B. modiolus closely resemble those of the
larvae of the other two members of the genus Brachidontes
described in the literature. In the early stages the larvae
of B. modiolus bear strongest resemblance to those of B.
recurvus while at later stages the more obvious resem-
blance is to the larvae of B. granulata. These findings tend
to reinforce the family or group relationships of these three
species. The most outstanding difference is in the devel-
opmental times, with B. modiolus settling the earliest of
the three.
This difference has been attributed to different temper-
ature regimes at which the larvae were reared. Brachi-
dontes recurvus was reared at 25°C, B. granulata at tem-
peratures between 12° and 16°C, and B. modiolus at 28°C.
ACKNOWLEDGMENTS
The National Marine Fisheries Service in Galveston,
Texas, supplied the monocultures used for feeding the
larvae in this study. The work was financially supported
by grants from the OAS (Barbados Office) and Board for
Postgraduate Studies of the University of the West Indies.
A. Fields & E. Moore, 1983
LITERATURE CITED
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Bayne, B. L. 1965. Growth and delay of metamorphosis of
larvae of Mytilus edulis. Ophelia 2:1-47.
BAYNE, B. L. (ed.). 1976. Marine mussels: their ecology and
physiology. Cambridge Univ. Press, London. 506 pp.
Campos, B. M. & L. RAMOoRINO. 1980. Larval and early ben-
thic stages of Brachidontes granulata (Bivalvia: Mytilidae).
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CHANLEY, P. 1970. Larval development of the hooked mussel,
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Mytilidae. Proc. Nat. Shellfish. Assoc. 60:86-94.
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CHANLEY, P. & M. CHANLEY. 1980. Reproductive biology of
Arthritica crassiformis and Arthritica bifurca, two commensal
bivalve molluscs (Leptonacea). N.Z. J. Mar. Freshwater
Res. 14(1):31-43.
CHANLEY, P. & W. A. VAN ENGEL. 1969. A three dimensional
representation of measurement data. Veliger 12(1):78-83.
Cor, W. R. 1953. Resurgent populations of marine inverte-
brates and their dependence on ocean currents and tidal
currents. Ecology 34:225-229.
CULLINEY, J. L. 1971. Laboratory rearing of the larvae of the
mahogany date mussel, Lithophaga bisulcata. Bull. Mar. Sci.
21(2):591-602.
Iwata, K. S. 1952. Mechanism of egg maturation in Mytilus
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Kuropa, T., T. Habe, K. OYAMA & C. LENT. 1971. The sea
shells of Sagami Bay. Biol. Labor. Imp. Household, Ma-
ruzen Co. Ltd., Tokyo. (Billing edition, English.) 489 pp.
LoosanorF, V. L. & H. C. Davis. 1963. Rearing of bivalve
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molluscs. /n: F. S. Russel (ed.), Advances in marine biology.
Academic Press, New York. Vol. 1. pp. 1-136.
LoosANoFF, V. L., H. C. Davis & P. CHANLEY. 1966. Di-
mensions and shapes of larvae of some marine bivalve mol-
luscs. Malacologia 4(2):351-435.
McLean, R. 1951. The Pelecypoda or bivalve molluscs from
Puerto Rico and the Virgin Islands. Scient. Surv. Puerto
Rico, XVII, Part 1:183 pp.
Morse, D. E., H. DuNcAN, N. HOOKER & A. Morse. 1977.
Hydrogen peroxide induces spawning in molluscs, with the
activation of prostaglandin endoperoxide synthetase. Science
196:298-300.
Morse, D. E., M. KAYNE, M. TIDYMAN & S. ANDERSON. 1978.
Capacity for biosynthesis of prostaglandin-related com-
pounds: distribution and properties of the rate-limiting en-
zyme in hydrocorals, gorgonians and other coelenterates of
the Caribbean and Pacific. Biol. Bull. 154:440-452.
RAVEN, C. P. 1958. Morphogenesis. The analysis of molluscan
development. Pergamon Press, New York. 310 pp.
SCHELTEMA, R. S. 1971. The dispersal of the larvae of shoal-
water benthic invertebrate species over long distances by
ocean currents. /n: D. J. Crisp (ed.), European marine bi-
ology symposium. Cambridge University Press, New York.
Vol. 4. pp. 7-28.
STANLEY, S. M. 1970. Relation of shell form to life habits in
the Bivalvia (Mollusca). Mem. Geol. Soc. Am. 125:496 pp.
STANLEY, S. M. 1972. Functional morphology and evolution
of byssally attached bivalve molluscs. J. Paleont. 46:165-
212.
WILSON, B. R. & E. P. HODGKIN. 1967. A comparative ac-
count of the reproductive cycles of five species of marine
mussels (Bivalvia: Mytilidae) in the vicinity of Fremantle,
Western Australia. Aust. J. Mar. Freshwater Res. 18:175-
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The Veliger 26(1):62-68 (July 1, 1983)
THE VELIGER
© CMS, Ine., 1983
A Comparison of the Species Richness and ‘Trophic
Roles of Gastropods and Chitons on Rocky Shores
of ‘Temperate and ‘Tropical West America
by
ALAN C. MILLER
Department of Biology, California State University, and Southern California Ocean Studies Consortium,
Long Beach, California 90840
Abstract.
I examined local species richness and trophic roles of gastropods and chitons in rocky
intertidal zones in Oregon, U.S.A., and in Costa Rica, Central America. Local species richness was
quite variable. Tropical sites did not always have more species nor was there a significant difference
in local species richness between regions. However, the species pool for the tropical transects (75) was
larger than for Oregon (44). The density of individuals per square meter was much greater in the
temperate sites.
Between-habitat diversity differences may account for most of the increase in over-all gastropod
species richness in Costa Rica. A regression analysis suggests that, among the variables tested, only the
number of gastropod refuges explains a significant amount of the variation in local species richness
among all sites.
An increase in carnivorous and carrion-eating snail species accounts for most of the expansion in
species richness in Costa Rica. This increase is principally in species that eat different food resources
than do temperate zone snails (e.g., sipunculans and small fishes) and species that feed on polychaetes,
gastropods, and dead or injured animals.
INTRODUCTION
MANny TAXA OF plants and animals, including gastropods
(THORSON, 1952; KOHN, 1971), have an increasing num-
ber of species along a decreasing latitudinal gradient
(PIANKA, 1966). This ecological phenomenon has been the
focus of many studies, and several hypotheses based on
physical and biological processes have been developed to
explain the generation and maintenance of this pattern
(PIANKA, 1966; PIELOU, 1975; HusTOoN, 1979).
One interesting question about this diversity pattern is
whether specific tropical habitats have a greater diversity
than similar habitats in the temperate zone. If so, what
ecological processes allow more species to co-occur in the
tropical habitats? Are there simply additional, different
microhabitats present within these “similar habitats” in
the tropics compared to the temperate zone? Are impor-
tant resources (such as food and habitat) more finely par-
titioned? Have physical and/or biological disturbances (2.e.,
' Contribution Number 14.
predation) kept species populations reduced in size so that
episodes of interspecific competition, if they occur at all,
are brief?
The general purpose of this study was to examine
quantitatively rocky intertidal areas in Oregon and Costa
Rica in order to provide answers to the following ques-
tions:
A. How does the gastropod and chiton species richness
in rocky intertidal areas differ between temperate and
tropical regions of West America?
B. What physical factors might explain some of the
variation in species richness between these areas?
C. Do tropical carnivorous gastropods use food re-
sources differently than temperate snails?
SITE DESCRIPTIONS ann METHODS
Table 1 describes the study sites chosen to sample areas
with different wave exposures and topographies. The Or-
egon sites were studied from April to August, during 1970,
1971, and 1972, the Costa Rican sites, in January and
February, 1972.
A. C. Miller, 1983
Page 63
Table 1
Description of the exposed-coast rocky intertidal study sites in Oregon and Costa Rica.
Tidal Transect name
Locality range (abbreviation) General description
Cape Arago, Oregon, U.S.A. 2.1m North Cove (NC) cliff with high splash pool
Middle Cove 1 (MC1) ledge area with no loose boulders
Middle Cove 2 (MC2) boulder field
South Cove (SC) bedrock with ledges and loose boulders
Cape Blanco, Oregon, U.S.A. 2.2 m Cape Blanco 1 (CB1) bedrock with ledges and loose boulders
Cape Blanco 2 (CB2) bedrock with ledges and loose boulders
Playa Hermosa, Guanacaste, Costa Rica 2.7 m Playa Hermosa 1 (PH1) bedrock with ledges and loose boulders
Playa Hermosa 2 (PH2) bedrock with ledges and loose boulders
Playa Hermosa 3 (PH3) bedrock with ledges
Samara, Guanacaste, Costa Rica Dell soa Samara 1 (S1) flat bedrock, ledges, and loose boulders
Samara 2 (S2) flat bedrock, ledges, and much algal turf
Samara 3 (S3) flat bedrock with ledges and tidepools
Quépos, Puntarenas, Costa Rica 2.5 m Quépos 1 (Q1) large boulders
Quépos 2 (Q2)
At each site, I chose a point at the high-tide drift line
and placed the base point for a transect a random number
(between O and 50) of meters from this point along the
drift line. I stretched a metric tape from the base point
toward the water’s edge at low tide and placed quadrats
(1 m X 1 m) across the transect line at arbitrarily set in-
tervals according to the length of the transect and the time
available to complete the work. For instance, South Cove
was sampled every meter along the transect line, while at
Samara 3, the interval was every 5 m. Within each quad-
rat I counted all snails, chitons, and nudibranchs and not-
ed their positions (under rocks, on top of rocks, etc.). I
did not include vermetid snails and octopuses. Due to
difficulties in differentiating the numerous small Fossarus
spp. from the similarly shaped and marked Littorina as-
pera in Costa Rica, I lumped these species. I had similar
problems distinguishing Collisella paradigitalis from C.
digitalis in Oregon so I lumped them together. When Fos-
sarus spp., Littorina spp., and limpets occurred in high
numbers, I counted them within six 10-cm? quadrats placed
randomly within the 1-m? quadrat and extrapolated their
densities to 1 m* from the average of these counts.
I quantified the intertidal height above O-m low tide at
20-cm intervals on the transect line within each sampled
quadrat using a simple surveying technique (placing a
pole on the transect line and sighting a horizontal line
from a marked position on this pole, a flag on a stationary
pole a known distance above the O-m tide point, and the
horizon). Based on C. M. Yonge’s method of zonation
(RICKETTS et al., 1968), I used 174 cm above mean lower
low water (O-m tide) as the separation height between
high and mid intertidal zones for Oregon. Since tropical
intertidal areas are not as well studied and the tidal datum
is different (mean low water spring tides), I based the
separation height between high and mid intertidal zones
in Costa Rica on gastropod assemblages. I determined it
bedrock with ledges and loose boulders
to be the lowest height reading (120 cm) of the quadrats
that contained only those gastropod species (Littorina as-
pera, L. modesta, Nerita funiculata, N. scabricosta, Planaxis
spp., Tegula pellisserpentis, Purpura pansa, and Acanthina
brevidentata) whose distributions are limited to the high
intertidal zone and the extreme upper portions of the mid
intertidal zone (KEEN, 1971; SPIGHT, 1976; GARRITY &
LEVINGS, 1981).
I quantitatively or qualitatively estimated some physi-
cal factors that might influence species richness. I quali-
tatively estimated wave exposure (0.0 = lowest exposure
to waves; 1.0 = greatest exposure) for each transect by
observing surf conditions and by assessing the number and
size of loose rocks. Using the average height measurements
for each quadrat, I computed the proportion of quadrats
that occurred below the high intertidal zone in each tran-
sect (Quépos 1 was excluded due to sampling problems).
As a measure of the availability of gastropod refuges, I
computed for each transect the proportion of quadrats in
which snails were found on the undersides of rocks or
ledges.
Since all of the values of these variables vary between
O and 1, I angularly transformed them before computing
a stepwise multiple regression with species richness. I in-
cluded a latitude variable in this analysis, computed as a
ratio of the transect’s latitude divided by 90°; I also an-
gularly transformed this ratio.
The diets of the carnivorous and carrion-eating gastro-
pods were determined from a literature review (MILLER,
1974), from field observations, and by collecting individ-
uals in the field, isolating them in containers of sea water
for up to 24 h, and then microscopically examining fecal
pellets for prey hard parts. I assigned the carnivorous snail
species to various diet categories based on the percentage
of occurrence of specific food items in their diets. If 75%
or more of the food items in a species’ diet were in one
Page 64
The Veliger, Vol. 26, No. 1
Table 2
A comparison of the species richness and density of gastropods and chitons in the Oregon and Costa Rican transects.
Oregon
NC MC1 MC2~ SC CB1
Number of quadrats 8 14 14 5 19
Species richness 13 18 28 36 19
XK + SEM 22.7 + 3.34
U-test
Number/m? 61 83 171 188 143
X + SEM 131.0 + 20.2
U-test
diet category, I assigned that species only to that diet cat-
egory. If less than 75% of the feeding observations were
in one category, I assigned the species to the two diet
categories that made up at least 70% of the diet. If the
two most common diet categories comprised less than 70%
of the observations, I included the third highest diet cat-
egory.
MILLER (1974) lists the chiton and gastropod species
discussed in this study as well as their abundances and
the diets of the carnivorous and carrion-eating snails. These
lists may be obtained from the author. Voucher specimens
reside in the author’s collection.
RESULTS
Species Richness
The number of species of gastropods and chitons is
extremely variable in both Oregon and Costa Rica (Table
2). The number of species found in a local area does not
differ significantly between regions. The density of gas-
tropods and chitons is, however, significantly greater in
the Oregon transects.
The species pool for the Oregon samples (44) is much
smaller than that for the Costa Rican samples (75); thus,
there is an increase in the number of gastropod species
with decreasing latitude when large geographic areas are
considered.
Physical Factors
In an attempt to ascertain what physical factors might
explain some of the variation in species richness among
the transects, I compiled a list of potentially important
variables (Table 3) that I was able to quantify or quali-
tatively estimate.
I chose wave exposure (WAVES) as a variable since
the degree of exposure of an intertidal area to wave shock
is important in determining what kinds of organisms occur
there (RICKETTS et al., 1968). I picked the proportion of
Costa Rica
PH1 PH2 PH3 S1 S2 $3 Qi Q2
14 15 13 23 25 32 14 9
27 28 15 33 34 29 38 26
28.8 + 2.43
N.S.
341 47 105 49 28 34 46 18
83.5 + 37.9
U = 40, P < 0.05
samples from below the high intertidal zone in a transect
(HT) as a variable because there is a trend of increasing
species richness with a decrease in intertidal height
(JOHNSON, 1970; MILLER, 1974; SpIGHT, 1977). The
presence of undersides of rocks, boulders, or ledges in-
creases the topographic complexity of an area and pro-
vides microhabitats for the snails that are more sheltered
from mortality factors like desiccation and wave shock
than areas with only flat bedrock (KOHN & LEVITEN,
1976; MENGE & LUBCHENCO, 1981). For this reason, I
calculated a refuge variable (REF) by computing the pro-
portion of quadrats in each transect that had undersides
of rocks or ledges occupied by gastropods. I included lat-
itude (LAT) as a variable since it could include some
biological and physical parameters that are different in
the tropics compared to the temperate zone, but which I
did not measure (PIANKA, 1966; Huston, 1979).
Although not a physical factor, I also used the number
of sampled quadrats (QUADS) as a variable since, at least
for Oregon, species richness (S) may be related to it in
my study (S = —8.66 + 25.8 log QUADS; t = 3.21, P <
0.025; R? = 0.72). For Costa Rica, none of the regression
analyses using log-transformed or untransformed values
of S and QUADS resulted in a significant regression or
an R? value greater than 0.14.
A comparison of each of the variables in Table 3 for a
significant difference between Oregon and Costa Rica in-
dicated that only “Latitude” was significantly different
(U = 48, P < 0.001).
I did a stepwise multiple regression using these vari-
ables to find out which ones might explain significant
amounts of the variation in species richness (S) among all
of the transects (excluding Quépos 1). The largest total
adjusted R’, 0.83, was obtained using the logarithm of
species richness; the only significant independent variable
was the gastropod refuge variable (F = 6.0, P < 0.05).
The regression equation was: log S = 0.004 QUADS —
0.003 LAT + 0.003 REF + 0.001 HT — 0.002
WAVES + 1.319.
A. C. Miller, 1983
Page 65
Table 3
Summary of the physical factor measurements and estimates, the latitudes, and the sample sizes of the Oregon and Costa
Rican transects.
Proportion of
Proportion of
quadrats below quadrats with Number of
high intertidal gastropod 1-m? quadrats
Transect Wave exposure zone refuges Latitude sampled
Oregon
North Cove 1.00 0.27 0.00 43,32° 8
Middle Cove 1 0.80 0.38 0.14 43.32° 14
Middle Cove 2 0.40 0.75 1.00 43.32° 14
South Cove 0.40 1.00 0.53 43.32° 51
Cape Blanco 1 0.80 0.70 0.26 42.50° 19
Cape Blanco 2 0.80 0.92 0.54 42.50° 13
Costa Rica
Playa Hermosa 1 0.60 0.57 0.50 10.50° 14
Playa Hermosa 2 0.60 0.84 0.40 10.50° 15
Playa Hermosa 3 0.80 0.60 0.08 10.50° 13
Samara 1 0.20 0.89 0.35 9.87° 23
Samara 2 0.40 0.97 0.60 9 :8ile 25
Samara 3 0.20 1.00 0.19 9.87° 32
Quépos 1 0.80 — 0.79 9.45° 14
Quépos 2 0.80 0.94 0.67 9.45° 9
The Between- and Within-Habitat
Components of Diversity
Total diversity in a large geographic region consists of
two components: within-habitat diversity and between-
habitat diversity (MACARTHUR, 1965). If within-habitat
diversity has contributed significantly to the larger species
pool in Costa Rica, then similar habitats should support
more diverse assemblages of gastropods and chitons there
than in Oregon. Two lines of evidence in my study suggest
that the within-habitat component is not as important as
the between-habitat component for rocky intertidal habi-
tats.
First, transects in Oregon and Costa Rica that are sim-
ilar in wave exposure, proportion of quadrats below the
high intertidal zone, and proportion of quadrats with gas-
tropod refuges (Table 3) have similar diversities (Table
2)—e.g., South Cove and Samara 2; Cape Blanco 2 and
Quépos 2. Second, the number of species found in indi-
vidual 1-m? samples is not significantly different between
the two regions (U = 37.5, P > 0.05). These values ranged
from 4.1 to 7.8 (X =5.8 + 0.59 SEM) in Oregon and
from 2.8 to 5.3 (X = 4.4 + 0.29 SEM) in Costa Rica.
Between-habitat diversity appears to be different be-
tween regions. To assess this, I compared for each region
the percentages of (1) omnipresent species, (2) species
found in all transects except one, and (3) species unique
to one transect (Table 4). These results suggest that tran-
sects in Oregon have more species in common and have
fewer unique species. This may mean that the transects
are sampling similar habitats in Oregon and more differ-
ent habitats in Costa Rica.
Comparison of the percentages of the species in each
transect that are also found in one or more other transects
(SALE, 1980) also suggests an increase in the between-
habitat component in Costa Rica. Oregon transects have
significantly greater percentages than Costa Rica (U =
44.5, P < 0.01). The average percentage is 93.1% for Or-
egon transects and 88.3% for Costa Rican transects.
Trophic Structure
In the trophic structure analysis, I lumped carnivorous
and carrion-eating snails together since I could not tell
whether snails known to feed on carrion would also eat
living prey. Some snails that normally attacked living prey
were observed eating dead animals.
Table 4
A comparison of the percentage of species found in all
transects, the percentage in all transects except one, and
the percentage unique to one transect.
Oregon Costa Rica
% omnipresent 9.1% 2.7%
% in all but one transect 34.1% 10.7%
% unique 29.5% 36.0%
The Veliger, Vol. 26, No. 1
Table 5
Comparison of the trophic characteristics of the assemblage of species in each transect.
Page 66
NG MCi MC2 SC _ CBI
No. herbivorous species 10 12 20 22 12
X + SEM SS OREe220)
No. carnivorous and
carrion-eating species 3 6 8 14 7
X + SEM Tell 22 1.5
Proportion of carnivorous and
carrion-eating individuals 06 03 .03 .06 .06
X + SEM 0.05 + 0.01
CB2 PH1 PH2 PH3 Si S2 S3 Qi Q2
14 14 7 10 22 21 13 20 13
16.2 + 1.6
8 13 11 5 11 13 16 18 13)
12,5 ae il.4
05 07 aSi/ 05 alts 2) 54 Lai .28
0.26 + 0.06
The assignment of some of the grazing mollusks to the
carnivorous or herbivorous trophic level is difficult since
some species may be indiscriminate grazers, feeding on
both plant and animal material. For instance, some species
of Calliostoma graze on sessile animals (MILLER, 1972;
PERRON, 1975); but I did not find animal remains in the
feces of seven C. ligatum from the Oregon transects. Ex-
cept for Placiphorella velata, which entraps and eats mobile
crustaceans (MCLEAN, 1962; Miller, personal observa-
tion), most chitons graze on plant material (references in
Morais e¢ al., 1980). However, there is evidence that some
species of Mopalia graze on sessile animals and algae
(BARNAWELL, 1960). In this study I have considered all
chitons except P. velata as herbivores, C. ligatum as an
herbivore, and all species of Cypraea as carnivores.
There is no significant difference in the number of her-
bivorous species found in transects in Oregon compared
to Costa Rica (Table 5; U=29, P > 0.05). However,
Costa Rican transects have significantly more carnivorous
and carrion-eating species than Oregon (U = 38, P <
0.05). The Costa Rican transects also have a larger pro-
portion of carnivorous and carrion-eating individuals than
Oregon transects (Table 5; U = 44.5, P < 0.01). The pro-
portion of carnivorous and carrion-eating species in the
species pool is 0.41 in Oregon and 0.52 in Costa Rica.
The Diets of Carnivorous and
Carrion-Eating Snails
Since the increase in species richness in Costa Rica
occurs primarily in carnivorous and carrion-eating species,
I examined the diets of these snails to compare food-re-
source use between temperate and tropical species (Table
6). The main differences are threefold increases in the
number of snail species eating polychaetes and gastropods
in Costa Rica compared to Oregon and the exploitation
by tropical snails of sipunculans and fishes, two food types
not used by Oregon gastropods.
There is also a large increase in species eating dead
material in the tropics, due mainly to the numerous species
of Columbellidae. Most columbellids are attracted to dead
and/or injured prey (Marcus & MARCUS, 1962; SPIGHT,
1976; HATFIELD, 1979; Miller, personal observation), but
not enough work has been done to show that columbellids
are only carrion-eaters.
DISCUSSION
I examined the gastropod and chiton species richness at
several similar, exposed-coast rocky intertidal zone sites
in Oregon and Costa Rica. Local species richness is quite
variable (Table 2). The tropical transects were not always
richer nor was there a significant difference in the number
of species found in Oregon and Costa Rican transects.
However, the density of gastropods and chitons was sig-
nificantly greater in the temperate areas (Table 2). The
total number of different gastropod and chiton species in
all Costa Rican transects (75) is much larger than in all
Oregon transects (44).
These results agree with SPIGHT’s (1977) comparisons
of prosobranch species richness at two Washington State
rocky intertidal locations and one Costa Rican site. The
Table 6
Number of carnivorous and carrion-eating gastropod and chiton species feeding in each diet category. * Indicates that
species exist but were not found in my samples.
Live,
mobile
Coelen- Sipun- Poly- crusta- Bar- Bi- Gastro- Bryo- Echino- Tuni- Para- Dead
Sponges terates culans chaetes ceans nacles valves pods zoans derms cates Fishes sitic animals
Oregon 3 2 0 4 1 5 3 1 1 0* 1 0 2 3
Costa Rica 1 1 2 13 0* 7 3 4 0 1 1 1 1 10
A. C. Miller, 1983
difference in the number of tropical prosobranch species
in Spight’s study (79) and mine (61) may be due to his
deliberate sampling of as many habitats as possible at this
one site (SPIGHT, 1976, 1977). It is possible that the Cape
Arago region in Oregon, where I found 25 prosobranch
species, has more habitats than the more wave-protected
Puget Sound area (Shaw Island) in Washington, where
Spight found 16 prosobranch species.
The between-habitat component of species diversity ap-
pears to contribute more than the within-habitat compo-
nent to the larger total species richness that I found in
Costa Rica. This suggests that I was sampling a greater
diversity of habitats in Costa Rica and agrees with SPIGHT’s
(1977) conclusion that there are more niches (defined by
substratum and intertidal height) in Costa Rica with no
temperate zone counterparts.
Although many different physical and biological factors
may control local species richness, the only significant
variable of those that I measured or estimated as explain-
ing significant amounts of variation in species richness
(Table 3) was the presence of gastropod refuges. The
availability of the undersides of rocks and ledges as shel-
ters from wave shock, UV radiation, insolation, desicca-
tion, and large, visual predators has also been found by
others to be important in controlling species diversity and
population sizes (KOHN & LEVITEN, 1976; JOKIEL, 1980;
MENGE & LUBCHENCO, 1981).
The most obvious differences between the trophic struc-
ture in Oregon and Costa Rica are the significant in-
creases in the tropical region in the number of species of
carnivorous and carrion-eating gastropods and in their
proportion of the total individuals. The number of her-
bivorous gastropod and chiton species per transect is also
greater in Costa Rica than in Oregon, but not signifi-
cantly. Three of the tropical carnivorous snail species use
food resources present in the Oregon rocky intertidal but
not eaten by Oregon snails (sipunculans and fishes) and
a large number (13) prey on polychaetes. There are also
substantial increases in the number of snail species eating
living gastropods (4) and dead or injured animals (10) in
Costa Rica.
Although the more diverse carnivorous gastropod as-
semblage in Costa Rica has large numbers of species shar-
ing some food resources (at least on a large scale) and
other species eating prey not consumed by Oregon species,
I do not have enough dietary information to conclude that
competition has been more important in structuring the
gastropod community in Costa Rica than in Oregon com-
pared to some of the other possible structuring forces, such
as predation (MENGE & LUBCHENCO, 1981).
ACKNOWLEDGMENTS
The fieldwork formed part of my Ph.D. dissertation re-
search. Travel and equipment funds were provided by a
National Science Foundation Grant (GA 29340), a Soci-
ety of Sigma Xi Grants-in-Aid of Research award, and
Page 67
the Department of Biology, University of Oregon. I ap-
preciate the advice and field assistance given to me by Drs.
Peter Frank, Susanne Lawrenz-Miller, Fred Bernstein,
John Cubit, Tom Niesen, and Tom Spight. I also thank
Dr. James McLean for helping with the identification of
many of the species and Alan Kohn and an anonymous
reviewer for their comments on the manuscript.
LITERATURE CITED
BARNAWELL, E. B. 1960. The carnivorous habit among the
Polyplacophora. Veliger 2:85-88.
Garrity, S. D. & S. C. Levincs. 1981. A predator-prey in-
teraction between two physically and biologically con-
strained tropical rocky shore gastropods: direct, indirect and
community effects. Ecol. Monogr. 51:267-286.
HATFIELD, E. B. 1979. Food sources for Anachis avara (Col-
umbellidae) and a discussion of feeding in the family. Nau-
tilus 93:40-43.
Huston, M. 1979. A general hypothesis of species diversity.
Am. Nat. 113:81-101.
JOHNSON, R. G. 1970. Variations in diversity within benthic
marine communities. Am. Nat. 104:285-300.
JoxieL, P. L. 1980. Solar ultraviolet radiation and coral reef
epifauna. Science 207:1069-1071.
KEEN, A. M. 1971. Sea shells of tropical West America: ma-
rine mollusks from Baja California to Peru. Stanford Univ.
Press, Stanford, Calif. 1066 pp.
Koun, A. J. 1971. Diversity, utilization of resources, and
adaptive radiation in shallow-water marine invertebrates of
tropical oceanic islands. Limnol. Oceanogr. 16:332-348.
Konun, A. J. & P. J. LEvITEN. 1976. Effect of habitat com-
plexity on population density and species richness in tropical
intertidal predatory gastropod assemblages. Oecologia 25:
199-210.
MacArTuHur, R. H. 1965. Patterns in species diversity. Biol.
Rev. 40:510-533.
Marcus, Ev. & Er. Marcus. 1962. Studies on Columbelli-
dae. Bol. Fac. Filos. Cienc. Letr. Univ. Sao Paulo, Brazil,
No. 261. Zoologia No. 24:335-402.
McLEan, J. H. 1962. Feeding behavior of the chiton Placi-
phorella. Proc. Malacol. Soc. Lond. 35:23-26.
MENGE, B. A. & J. LUBCHENCO. 1981. Community organi-
zation in temperate and tropical rocky intertidal habitats:
prey refuges in relation to consumer pressure gradients. Ecol.
Monogr. 51:429-450.
MILLER, A. C. 1972. Observations on the associations and
feeding of six species of prosobranch gastropods on antho-
zoans. In: G. J. Bakus (ed.), Marine studies on the north
coast of Jamaica. Atoll Res. Bull. 152:4-5 (abstract).
Mixer, A. C. 1974. A comparison of gastropod species di-
versity and trophic structure in the rocky intertidal zone of
the temperate and tropical West Americas. Ph.D. thesis
Biology, Univ. Oregon, 143 pp.
Morris, R. H., D. P. ABporr & E. C. HADERLIE. 1980. In-
tertidal invertebrates of California. Stanford Univ. Press,
Stanford, Calif. 690 pp.
PERRON, F. E. 1975. Carnivorous Calliostoma (Prosobranchia:
Trochidae) from the northeastern Pacific. Veliger 18:52-54.
PIANKA, E. R. 1966. Latitudinal gradients in species diversity:
a review of concepts. Am. Nat. 100:33-46.
PrELou, E.C. 1975. Ecological diversity. Harper & Row, New
York. 165 pp.
RickeTTs, E. F., J. CALVIN & J. W. HEDGPETH. 1968. Be-
Page 68
ihe Veligery Vola ZowNoml
tween Pacific tides. Stanford Univ. Press, Stanford, Calif.
614 pp.
SALE, P. F. 1980. The ecology of fishes on coral reefs. Ocean-
ogr. Mar. Biol. Ann. Rev. 18:367-421.
Spicut, T. M. 1976. Censuses of rocky shore prosobranchs
from Washington and Costa Rica. Veliger 18:309-317.
SPIGHT, T. M. 1977. Diversity of shallow-water gastropod
communities on temperate and tropical beaches. Am. Nat.
111:1077-1097.
TuHorsON, G. 1952. Zur jetzigen Lage der marinen Bodentier-
Okologie. Verh. de Deutsch. Zool. Ges. 1951, Zool. An-
zeiger Suppled. 16:276-327.
The Veliger 26(1):69-70 (July 1, 1983)
THE VELIGER
© CMS, Inc., 1983
Range Extensions of ‘Three Opisthobranch Mollusks
to the San Diego—La Jolla (California)
Ecological Reserve
HANS BERTSCH!
Instituto de Investigaciones Oceanologicas, Universidad Autonoma de Baja California,
Apartado Postal 453, Ensenada, Baja California, Mexico
TOM SMITH
917 Thomas, Apartment 19, San Diego, California 92109
SINCE JUNE, 1980, we have studied the subtidal fauna (by
scuba diving) off La Jolla Shores Beach, La Jolla, Cali-
fornia (32°51’-52’N; 117°15’-16’W) in the San Diego-
La Jolla Ecological Reserve, within which collecting of
any kind is prohibited. The bottom is a sandy habitat that
gently slopes to about 12 m, and then precipitously, at 60°
to 90° angles, drops into the La Jolla Branch of the La
Jolla Submarine Canyon. The cliff faces and ledges of the
canyon at 12.2 to 18.3 m consist of soft mudstone. Al-
though this habitat supports a generally depauperate
opisthobranch fauna, three of the opisthobranch species
observed constitute southward range extensions.
Aglaja ocelligera (Bergh, 1894)
The reported range of Aglaja ocelligera (Cephalaspidea :
Aglajidae) is from southern British Columbia, Canada, to
Santa Cruz Island and Coal Oil Point, Santa Barbara
County, California (SPHON & LANCE, 1968, p. 76; SPHON,
1972, p. 55; GOSLINER, 1980; BEHRENS, 1980, p. 32).
The following records from La Jolla Canyon extend
the range southward more than 250 km:
(1) One specimen; 10 mm long, 9.1 m deep; 8 November
1981.
"U.S. mailing address: 416 W. San Ysidro Blvd., K-229, San
Ysidro, California 92073.
(2) Three specimens; 15 mm, 18.3 m deep; 16 mm and
eggs, 15.2 m deep, inside the stomach of Astropecten
armatus; and 20 mm, 7.6 m deep; 25 December 1981.
(3) One specimen; 20 mm, 13.1 m deep; 7 February 1982.
The finding of one specimen inside the sea star Astro-
pecten armatus Gray, 1840, is another record of predation
upon an opisthobranch, a group considered to have few
natural predators. MAUZEy et al. (1968) reported that in
the Puget Sound region, another sea star, Crossaster pap-
posus (Linnaeus, 1767), fed upon Aglaja diomedea.
Flabellina price: (MacFarland, 1966)
The known northern range limit of Flabellina pricei
(Nudibranchia : Aeolidacea: Flabellinidae) (generic
placement follows GOSLINER & GRIFFITHS, 1981) has been
expanded from the type locality of Monterey, California
(MacFarRLAND, 1966, p. 316), to Duxbury Reef, Marin
County, California (GOSLINER & WILLIAMS, 1970, p. 177),
and to Pearse Island, northern British Columbia, Canada
(LAMBERT, 1976, p. 295). Its known southern range limit
is Point Fermin, San Pedro, Los Angeles County, Cali-
fornia (SPHON, 1972, p. 60).
The following specimens extend its known range south-
ward about 145 km to La Jolla Canyon:
(1) Three specimens; 17 mm long, 10 m deep; 13 mm,
15.2 m deep; and 18 mm, 8.5 m deep; 14 May 1982.
Page 70
Cerberilla mosslandica McDonald & Nybakken, 1975
The known distribution of Cerberilla mosslandica (Nu-
dibranchia : Aeolidacea: Aeolidiidae) is restricted to the
type locality of Monterey Bay, in central California, from
16 to 63 meters of water. The specimens collected by the
Moss Landing Marine Laboratory benthic sampling team
ranged from 5 to 9 mm in total length when alive.
The following animal seen in the La Jolla Canyon
represents a southern range extension of more than 550
km, its first reported occurrence elsewhere than the type
locality, a new size record, and a slightly shallower bathy-
metric distribution:
(1) One specimen; 18 mm long, 12.2 m deep; 16 July
1982.
ACKNOWLEDGMENTS
The present study was completed under the auspices of
the Benthic Ecosystems Project of Baja California, sup-
ported by the Secretary of Public Education and the Au-
tonomous University of Baja California, Mexico.
LITERATURE CITED
BEHRENS, D. W. 1980. Pacific coast nudibranchs: a guide to
the opisthobranchs of the northeastern Pacific. Sea Chal-
lengers, Los Osos, Calif. 112 pp.
BERGH, L.S. R. 1894. Reports on the dredging operations off
the west coast of Central America to the Galapagos, to the
The Veliger, Vol. 26, No. 1
west coast of Mexico, and in the Gulf of California, in
charge of Alexander Agassiz, carried on by the U.S. Fish
Commission Steamer “Albatross,” during 1891, Lieut.
Commander Z.L. Tanner, U.S.N., commanding. Bull. Mus.
Comp. Zool. (Harvard) 25(10):125-233.
GosLINER, T. M. 1980. Systematics and phylogeny of the
Aglajidae (Opisthobranchia: Mollusca). Zool. J. Linn. Soc.
68:325-360.
GOSLINER, T. M. & R. J. GRIFFITHS. 1981. Description and
revision of some South African aeolidacean Nudibranchia
(Mollusca, Gastropoda). Ann. S. Afr. Mus. 84(2):105-150.
GosLINER, T. M. & G. C. WiLiiams. 1970. The opistho-
branch mollusks of Marin County, California. Veliger 13(2):
175-180.
LAMBERT, P. 1976. Records and range extensions of some
northeastern Pacific opisthobranchs (Mollusca: Gastropo-
da). Can. J. Zool. 54:293-300.
MAcFARLAND, F. M. 1966. Studies of opisthobranchiate mol-
lusks of the Pacific coast of North America. Calif. Acad.
Sci. Mem. 6:xvi + 546 pp.
Mauzey, K. P., C. BIRKELAND & P. K. DAYTON. 1968. Feed-
ing behavior of asteroids and escape responses of their prey
in the Puget Sound region. Ecology 49(4):603-619.
McDOona.p, G. & J. NYBAKKEN. 1975. Cerberilla mosslandica,
a new eolid nudibranch from Monterey Bay, California.
Veliger 17(4):378-382.
SPHON, G. G. 1972. An annotated checklist of the nudibranchs
and their allies from the west coast of North America.
Opisthobranch Newsletter 4(10/11):53-79.
SPpHON, G. G. & J. R. LANcE. 1968. An annotated list of
nudibranchs and their allies from Santa Barbara County,
California. Proc. Calif. Acad. Sci. 36(3):73-84.
The Veliger 26(1):71-72 (July 1, 1983)
THE VELIGER
© CMS, Inc., 1983
NOTES, INFORMATION & NEWS
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CATE, J. M. 1962. On the identification of five Pacific Mitra. The Veliger 4(3):132-
B34.
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YONGE, C. M. & T. E. THOMPSON. 1976. Living marine molluscs. Collins,
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CONTENTS— Continued
Comparison of northern and southern populations of Epztonium tinctum (Car-
penter, 1864) on the California coast
CAREY ARES CH 1S MIIAGEty AND NYY Gn RIENYsE/ RO eae ee eee
The reproductive cycle of the trochid gastropod Oxystele variegata (Anton,
1839)
M. ALPS JOSKA ANDGs) Ma BRYANGEIN. ieeean kre rica eee eh hy ices aoe eet ear
The larval biology of Brachidontes modiolus (Linné, 1767) (Bivalvia: Mytili-
dae)
ANGELACFIEL DS! AND SEUNAGNIOORE = ye ia erent ica ele ene
A comparison of the species richness and trophic roles of gastropods and chitons
on rocky shores of temperate and tropical west America
ALAN C.JMILGER TS oo ere Sei oh eet ath ded oes Sed big cc Sa ge er
Range extensions of three opisthobranch mollusks to the San Diego—La Jolla
(California) Ecological Reserve
EVANS) BERTSCH AND) (OM: SS MAHHO YE 2 Ge 4a5.4 a mie cle se ee ne oe
Notes, Information & News
37
47
52
62
oe ISSN 0042-3211 _
0, Oo /
THE
VELIGER
A Quarterly published by
CALIFORNIA MALACOZOOLOGICAL SOCIETY, INC.
Berkeley, California
R. Stohler, Founding Editor
Volume 26 October 3, 1983 Number 2
CONTENTS
Radular patterns, systematics, diversity, and ecology of deep-sea limpets.
CAROLE S. HICKMAN
Additions to the opisthobranch mollusk fauna of Marin County, California, with
notes on the biology of certain species.
VIN TELIL TAIN 1835." NNSKCH SO EMT Gel A PON tee eS en eo 93
Specialized feeding in mitrid gastropods: evidence from a temperate species,
Mitra idae Melvill.
AELANGHUKUVAMACAND) JAMES INYBAKKEN ©... 20. ..05.0.05-.0. 0.54500 96
Homing in the West Indian chiton Acanthopleura granulata Gmelin, 1791.
JDUANWIOD) IVCKORS S08 ss ORR a a eta Oy) ees nm ne EAN AI 101
Aspects of reproduction in some enoploteuthid squids from Hawaiian waters.
ILIA IML: IKOUWIGTETST Ls, ile dial i cata ered er ape LaPeer > te ed mea eae 106
Shell repair frequencies of two intertidal gastropods from northern California:
microhabitat differences.
RON AGEIAN GIS | GEE RG i meme ein, «Ge OM cM ote MMR ING AR ake, NS)
Morphological divergence and predator-induced shell repair in Alia carinata
(Gastropoda: Prosobranchia).
JULIA BERGMAN, JONATHAN B. GELLER, AND VICTOR CHOW ........... 116
Thermal effects on some mangrove mollusks.
ION CAV OOM GHOOPAND ESE ANOR (CHIN eels. ay laa ary sys ees eee ee 119
CONTENTS — Continued
The Veliger (ISSN 0042-3211) is published quarterly on the first day of July, October,
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THE VELIGER
Scope of the journal
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This is meant to make facilities available for publication of original articles from a
wide field of endeavor. Papers dealing with anatomical, cytological, distributional, eco-
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Carole S. Hickman, University of California, Berkeley
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Frank A. Pitelka, University of California, Berkeley
Peter U. Rodda, California Academy of Sciences, San Francisco
Clyde F. E. Roper, National Museum of Natural History, Washington
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The Veliger 26(2):73-92 (October 3, 1983)
THE VELIGER ©
© CMS, Inc., 1983
Radular Patterns, Systematics, Diversity, and
Ecology of Deep-Sea Limpets
by
CAROLE S. HICKMAN
Department of Paleontology, University of California, Berkeley, California 94720
Abstract.
Sixteen distinct radular patterns from deep-sea limpets are illustrated and discussed. Two
of the patterns are docoglossan, nine are rhipidoglossan, and five do not fit the standard classification
of gastropod dentition. The diversity of gastropods that have converged on limpet shell form is re-
markable. The animals occur in three major deep-sea settings: at hadal depths in eutrophic nearshore
trenches; at eutrophic hydrothermal vents at divergent oceanic plate boundaries; and associated with
isolated ‘‘food falls” in oligotrophic regions of the bathyal and abyssal zone. Many of the taxa are
opportunistic specialists on unusual substrates such as wood, sea-grass rhizomes, cephalopod beaks,
empty polychaete tubes, and empty skate or shark egg cases. Radular morphology is not, however,
convergent in groups that have converged on the same unusual substrates. Different taxa have adopted
alternative morphological solutions to using the same substrate. The high diversity of minute limpets
in the deep sea today is equalled only by the diversity of minute limpets in the initial Cambrian
radiations of the Mollusca. The protective function of limpet shell geometry that is invoked for familiar
shallow-water intertidal limpets is not applicable to minute deep-sea limpets or to Cambrian limpets.
Freedom to experiment with reproductive and respiratory modes is proposed as an important factor in
the evolution of limpet geometry.
Radular characters provide powerful taxonomic tools at the family level, and above, because they
reflect fundamentally different groundplans. At the generic and specific levels, however, radular char-
acters must be used with caution because the tendency for morphology to degenerate or fail to develop
exceeds evolutionary “perfection” or “fine-tuning” of elaborate structure.
Pseudococculinidae fam. nov. is proposed to provide consistent familial level distinction of groups
separated by major discontinuities in radular patterns.
INTRODUCTION
THE TERM “limpet” is applied to a variety of gastropods
with low, broadly conical shells. It denotes not only a shell
form that has evolved numerous times within the class,
but also the accompanying habit of clinging or clamping
to rocky substrates (YONGE & THOMPSON, 1976, p. 51).
Accordingly, functional interpretations of the limpet shell
form have emphasized the theme of protection at the ex-
pense of mobility (YONGE & THOMPSON, 1976, p. 265).
Protection has been identified as resistance to predation
as well as resistance to the physical stresses of the inter-
tidal zone on rocky coasts: notably wave shock, tempera-
ture, desiccation, and salinity stress (VERMEIJ, 1978;
BRANCH, 1981).
Not all limpets live on rocky substrates, however. The
purpose of this paper is to call attention to the extraor-
dinary taxonomic diversity of gastropods that have adopt-
ed this shell form in deep water (below 200 meters). At
least 15 families are involved. Many of the deep-sea lim-
pets have minute shells (less than 5 mm long) and are
poorly studied anatomically. Examination of their radulae
has revealed striking differences within taxa heretofore
considered to be closely related. Several of the radular
patterns are so unique that they do not fit the standard
classification and terminology used to describe gastropod
radulae.
Although radular anatomy will contribute substantially
to evaluating the taxonomic relationships of deep-sea lim-
pets, comprehensive systematic revision will require a great
deal of further study of the soft anatomy. However, it is
appropriate at this time to summarize and illustrate the
range of radular morphology and correspondingly high
diversity of feeding modes in order to stimulate further
interest in the biology and systematics of these animals.
Page 74
Many are restricted to unusual substrates in the deep sea,
including water-logged wood, rhizomes of Thalassia, emp-
ty polychaete tubes, empty skate egg cases, cephalopod
beaks, and bone.
There are three major deep settings in which most of
the diversity and abundance of limpets is concentrated.
None of these settings is typical of the deep sea in terms
of the main body of ecological theory concerning this vast
portion of the marine realm. The first is the eutrophic
nearshore trench or basin that predictably receives large
volumes of plant material of terrestrial origin. At low
latitudes where trenches border salt marsh or mangrove
areas of high productivity, such as the Puerto Rico and
Cayman Trenches, the abundance of terrestrial material
transported in by turbidity flows may be particularly high
(WoLFF, 1976, 1979, 1980; GEORGE & HiGGIns, 1979).
The second is the eutrophic setting created by hydrother-
mal vents, also regions of high productivity, although based
on a chemosynthetic rather than photosynthetic pathway
(JANNASCH & WIRSEN, 1979, 1981; RAU & HEDGES, 1979;
Kart et al., 1980; CAVANAUGH et al., 1981; Rau, 1981).
The kinds of limpets that are associated with these first
two kinds of food sources are taxonomically distinct. Both
groups, however, share opportunistic characteristics that
are not normally associated with deep-sea organisms.
Many of the limpets in the first group also occur in a
third and more transient setting: as colonists of relatively
large “low-quality food falls” (sensu STOCKTON & DE-
Laca, 1982) in the form of waterlogged wood that pe-
riodically reaches the ocean floor in otherwise oligotrophic
regions. The wood-ingesting limpet guild occurs consis-
tently with other invertebrates that also are specialized
starting points in the conversion of wood to animal bio-
mass, most notably wood-boring bivalves of the genus Xy-
lophaga (TURNER, 1973).
A striking feature of many deep-sea limpets is the small
size of the shell. It is potentially of significance to paleon-
tological and malacological debates about the origins and
early diversification of the Mollusca. The earliest fossil
record of mollusks, not only gastropods but also Mono-
placophora and a number of groups of questionable affin-
ities, is dominated by small limpets. Many of these minute
forms may have been associated with unusual substrata
or may even have lived infaunally. The protective. inter-
pretation of shallow-water modern limpet shell form would
not apply at this scale. The discovery of a minute: (less
than 2.5 mm maximum shell length), monoplacophoran
limpet associated with small rocks within muddy sub-
strates at the edge of the continental shelf (MCLEAN, 1979)
suggests another mode of life—a means of being function-
ally epifaunal in an infaunal environment. Thus, an anal-
ysis of available ecological data on deep-sea limpets and
their unconventional substrates provides the basis for some
new hypotheses for functional interpretation of the minute
limpet form in early mollusks, even though Recent deep-
sea limpets are secondarily flattened.
The Veliger, Voll 2633NogZ
MATERIALS anp METHODS
The following survey of deep-sea limpet radulae is based
on extractions from both wet and dry material from nu-
merous sources (see acknowledgments). Dry specimens
were rehydrated in saturated trisodium phosphate prior
to maceration. Radulae from both wet and dry specimens
were removed from the buccal mass following treatment
in a 10% solution of sodium hydroxide. All radulae were
removed before the buccal mass was completely broken
down, so that the chitin of the teeth and radular mem-
brane did not come into direct contact with the caustic
solution. Radulae were washed thoroughly in distilled
water and dehydrated through an ethanol series from 70%
to 100% prior to air drying and mounting for scanning
electron microscopic (SEM) examination. Before drying,
radulae were cleaned by brief immersion in an ultrasonic
cleaner. The intensity of cleaning was based on a combi-
nation of the robustness of the radula and its ability to
withstand ultrasonication, and the amount of extraneous
material on the teeth.
Radulae were manipulated during air drying to expose
maximum dentition, which involves laying back the mar-
ginal tooth complexes in the rhipidoglossan types. Dry
radulae were transferred to SEM stubs and mounted on
a thin film of Elmer’s Glue® thinned with distilled water
and allowed to dry until only slightly tacky. It is important
not to drop the radula onto wet glue, and even when the
glue appears dry, good bonding may be achieved between
the radula and the SEM stub by breathing gently on the
preparation. All handling of radulae was performed using
flexible minuten nadlen, extremely fine insect pins, glued
to 2-mm-diameter wooden splints.
- All specimens were coated with 200-400 A of gold and
viewed at accelerating voltages of 10 kV or less to mini-
mize charging and specimen damage. Preparations illus-
trating each major radula type were rotated into a stan-
dard orientation relative to the electron beam, with the
stage maintained flat. The orientation selected allows a
diagonal presentation that maximizes areal coverage and
resolution. All manipulations were made mechanically with
the microscope stage, and not electronically or by scan
rotation, to ensure consistent shading. Stereographic pairs
were taken of each radula to provide further basis for
interpretation. This is particularly important in the anal-
ysis of unusual radulae in which the topographic differ-
ences between teeth of different types may be considerable,
but are not readily perceived, in single electron images.
Scanning electron microscopy is a valuable tool in the
study of deep-sea limpet radulae, because their minute
size places a great deal of morphological detail beyond the
resolvable range of light microscopy. Previous treatments
of the taxonomy of deep-sea limpet taxa that include rad-
ular data have been illustrated by line drawings that are
ambiguous, imprecise, and frequently erroneous in inter-
pretation. The illustrations that follow will help in the
C. S. Hickman, 1983
reinterpretation of many drawings in the literature and
will enable future workers who do not have access to SEM
to interpret light microscope preparations.
The selection of radular material for illustration is made
on morphological rather than systematic or typological
grounds. The objective is to present the best possible il-
lustration of all the major radular patterns known from
the deep sea. In several cases, distinctive patterns are
known from a single species and represent the only ma-
terial available. In most instances, however, the patterns
are known from a number of species, and the material
illustrated is chosen to show central tendencies and ex-
tremes of variation. Because the radulae of type species
do not necessarily illustrate central tendencies, they are
included only where morphologically appropriate.
RADULAR MORPHOLOGY anp PATTERNS
Fissurellid Limpets (Figures 1, 2, 3)
The keyhole limpets are, as a family, predominantly
shallow-water, hard-substrate dwellers. Those forms that
do occur in deep water are particularly interesting because
their radulae differ from the radulae of shallow-water
members of the family, although little is known of their
feeding habits or substrate preferences. The radulae of
three deep-sea fissurellids are illustrated in Figures 1-3.
Puncturella: Puncturella Lowe, 1827 (Figure 1) has the
most typically fissurellid radula, and some species in the
genus, including the type, P. noachina (Linné, 1771), are
not restricted to deep water, but occur intertidally in the
high latitude portion of their range. The massive, strong-
ly cusped outer lateral teeth and reduced prominence of
the rachidian and inner lateral teeth are hallmarks of the
fissurellid radula. The radula figured here lacks the pro-
nounced asymmetry that is characteristic of many shal-
low-water fissurellids (HICKMAN, 1981), but it is not
known whether lack of asymmetry is universal in Punc-
turella.
Fissurisepta: Fissurisepta Seguenza, 1853 (Figure 2), on
the other hand, displays both the prominent outer lateral
tooth and the asymmetry. Note that each of the left inner
lateral teeth is more anteriorly positioned than the right
inner lateral in the same row. This skewing of rows is an
accommodation that permits an alternating or zipper-like
close-packing arrangement of the large outer lateral teeth
when the radula is retracted or folded for storage when
the animal is not feeding (HICKMAN, 1981). The combi-
nation of serrate cusps on the inner lateral teeth and the
absence of both shaft and cusp on the rachidian in this
radula is, however, unique.
Zeidora: The radula of the deep-water genus Zezdora A.
Adams, 1860 (Figure 3) is even more unusual, as judged
from examination of one unidentified species. There is no
trace of a rachidian tooth, and the outer lateral tooth is of
Page 75
an unusual form in that there is a thin, secondary shaft
and cusp that appear to be fused to the main body of the
tooth. This suggests that the massive fissurellid outer lat-
eral may, evolutionarily, be a compound tooth resulting
from the fusion of what were once distinct elements. The
radula is also unusual in that the form of the asymmetry
is reversed (2.e., rows are skewed so that the right lateral
and marginal teeth fold into the tooth row anterior, rather
than posterior to the left lateral teeth in the same row).
Based on shell characters, Zezdora has been interpreted to
be the most primitive genus in the Fissurellidae (FAR-
FANTE, 1947), but the radula of the species investigated is
not of a generalized form that would readily permit der-
ivation of other forms of fissurellid dentition.
Limpets Questionably Allied to the
Fissurellidae (Figures 4, 5)
Laevinesta: The monotypic genus Laevinesta Pilsbry &
McGinty, 1952, based on Nesta atlantica Farfante, 1947,
is so bizarre in its radular morphology that it can no
longer be included comfortably in the Fissurellidae, al-
though it may be of fissurellacean derivation (HICKMAN,
1983). The radula (Figure 4) bears little resemblance to
that of any living gastropod in its combination of a low
central field of teeth with prong-like cusps and its flanking
fields of plates. The presence of two, long and slender
marginal teeth in each half row does identify it as being
of rhipidoglossan derivation, but it is so highly modified
and distantly removed morphologically from all other gas-
tropod radulae that it is impossible to ascertain its affin-
ities. The fragile shell is wholly internal, but has a mar-
ginal slit and selenizone that are of fissurellid appearance.
The animal occurs on sponges and presumably feeds upon
them, although the precise nature of the association is not
documented.
The generalized form of the radula of Laevinesta, in
which fields of robust plates replace normal teeth, repre-
sents a grade of radular morphology that has been at-
tained independently in several other major groups of deep-
sea limpets (e.g., Bathysciadiidae, Addisoniidae) that are
associated with unconventional substrates.
Galapagos Rift slit lmpet: Another small, emarginate,
slit limpet that has a shell of fissurellid appearance occurs
at deep-sea hydrothermal vents in the Galapagos Fracture
Zone, where it has been recovered from washings of larger
sessile mega-invertebrates (ANONYMOUS, 1980). The shell
is unusual in that it is asymmetric, with the slit and se-
lenizone forming an acute angle with the line bisecting
the shell. It is the radula (Figure 5) that leads to serious
questions about the affinities of the animal. It is rhipi-
doglossan, but there is no asymmetry, no enlarged outer
lateral tooth, and no reduction of the prominence of the
central tooth field. In fact there is an abnormally high
number of lateral teeth (9 per half row in contrast to the
traditional 4 of the fissurellid radula). There are other
The Veliger, Vol. 26, No. 2
Cy Ssilickman, 1983
Page 77
peculiarities of the radula that will be discussed in greater
detail by Turner and Hickman (in preparation).
Patellacean Limpets (Figures 6, 7, 8)
Patellacean limpets, like fissurellids, occur primarily in
rocky intertidal habitats, with several offshoots that are
specialized for life in the deep sea: notably Pectinodonta
Dall, 1882, in the Acmaeidae, and Propilidium Forbes &
Hanley, 1849, Bathylepeta Moskalev, 1979, and other
members of the family Lepetidae. Deep-sea patellaceans
have radulae that are at once recognizable under the light
microscope as docoglossan, a highly specialized form of
gastropod dentition in which a few, heavily cusped teeth
appear brown or black pigmented, due to the addition of
iron salts that substantially increase tooth hardness. The
radulae of deep-sea patellaceans do, however, contain some
peculiarities that are related primarily to fusion of ele-
ments.
Pectinodonta: This genus comprises a small, but widely
distributed, group of deep-sea species that are primarily
members of the wood-ingesting guild. They are frequently
recovered from wood (WOLFF, 1979; personal observa-
tion) that they cohabit with both cocculinid and pseudo-
cocculinid limpets. The radula of Pectinodonta (Figure 6)
is unusual in the elongation of the third lateral tooth into
a multicusped, curved, serrate unit that compresses the
first and second lateral teeth, which form, along with the
third lateral, a curved diagonal cutting edge with an ap-
pearance similar to that of a wood rasp (SCHOOLEY et al.,
1982; HICKMAN, 1982). The teeth are set at a steeply
acute angle to the longitudinal axis of the radula. Al-
though each pair of compound cutting edges appears to
be identical with the pairs anterior and posterior to it,
careful inspection of Figure 6 shows that pairs are not
strict mirror images and that one tooth set in each pair
lies either slightly anterior to or slightly posterior to the
other. There is an alternation along the length of each
half row of the radula in anterior vs posterior placement.
WoLFF (1979) has reported scars on wood from which
Pectinodonta has been recovered. These probably repre-
sent homing depressions produced as a result of activity
distinct from feeding. The plane of the aperture is not flat
in some species but curved, presumably to conform to a
curved, wood surface.
CHRISTIAENS (1979) reviewed the species of Pectino-
donta and concluded that, because of the close similarity
of shell form with that of some cocculinid limpets, some
species originally assigned to Cocculina are actually Pec-
tinodonta. However, LINDBERG (1979) has noted that, even
without animals and radulae, the genera are easily sepa-
rated by major differences in shell structure.
Lepetid limpets: Although the family Lepetidae is by no
means restricted to deep water, the comprising species are
predominantly subtidal in habit and restricted to cold
water, primarily at high latitudes, where they occur on
pebbles and cobbles at the sediment-water interface
(YONGE, 1960). The ctenidium is lacking (lost?) in lepe-
tids, but without development of secondary gills, which
YONGE (1960) has interpreted as requiring continuous
submergence while freeing the animal for life on muddy
substrates, an impossibility for so many gastropods that
face the problem of sediment clogging of the respiratory
apparatus. Although no firm evidence supports YONGE’S
scenario for the evolution of the situation in which spe-
cialized respiratory structures are lacking (the absence of
morphology is always difficult to interpret), a number of
unrelated deep-sea limpet groups discussed below also lack
ctenidia or secondary gills. MOSKALEV (1977) has de-
scribed species of Lepetidae that are restricted to deep-sea
trenches at depths in excess of 5000 m.
Little is known of the diet of lepetids. YONGE (1960)
has observed that Lepeta (Cryptobranchia) concentrica
(Middendorff, 1847) feeds on organic detritus that settles
out of the water column. The lepetid radula is complicat-
ed, and drawings in the literature, although sometimes
meticulous (MOSKALEV, 1977), are difficult to interpret.
For comparative purposes it is particularly important to
Explanation of Figures 1 to 8
Figure 1. Puncturella sp. Zoological Museum, University of Co-
penhagen, Galathea Station 436. Bar = 100 um.
Figure 2. Fissurisepta granulosa Jeffreys, 1882. Specimen pro-
vided by A. Warén; Biological Station, University of Bergen
Reference Number E39-71. Bar = 20 um.
Figure 3. Zeidora sp. U.S. National Museum (USNM) 761482.
Bar = 40 wm.
Figure 4. Laevinesta atlantica (Farfante, 1947). USNM 792397.
Bar = 100 um.
Figure 5. Galapagos Rift slit limpet, gen. et sp. nov. Deep Sea
Research Vessel (DSRV) Alvin Dive 733. Bar = 40 um.
Figure 6. Pectinodonta n. sp. U.S. Fish and Wildlife Service
Bureau of Commerical Fisheries, R/V Oregon II, Station 11230.
Bar = 100 um.
Figure 7. Lepeta (Cryptobranchia) concentrica Middendorff, 1847.
University of California Museum of Paleontology (UCMP) 2896.
Bar = 100 um. Dentition from posterior portion of radula. Note
the central and lateral teeth are still fused into a single unit that
is beginning to separate medially.
Figure 8. L. (C.) concentrica. Dentition from the anterior end of
the same radula illustrated in Figure 7. Note that the laterals
are distinct and separate from the double central tooth. C =
central; L = lateral; M = marginal. Bar = 100 um.
The Veliges VorZouNow
fl
ied
C. S. Hickman, 1983
view the radula at a standardized point in ontogeny due
to variation in the amount of fusion of elements along the
length of the membrane. This is illustrated by two views
of the radula of L. (C.) concentrica: in Figure 7, the po-
sitionally central and lateral teeth are fused into a single
element, although they are beginning to separate medially;
and the marginal teeth are separate and fully formed.
These teeth are from the posterior portion of the radula.
In Figure 8, from the anterior end of the same radula, the
teeth are fully formed and worn from use; and the central
tooth is double and flanked by worn lateral teeth as well
as by worn marginals.
Although I have not been able to examine the radulae
of any of the deep-sea lepetid species, drawings in the
literature (e.g.. MOSKALEV, 1977; DELL, 1956) suggest a
basic plan of dentition comparable with that of the shal-
low-water species discussed above and illustrated in Fig-
ures 7 and 8.
Bathysciadiid Limpets (Figures 9, 37a, b)
The family Bathysciadiidae Dautzenberg & Fischer,
1901, and the genus Bathysciadium Dautzenberg & Fisch-
er, 1901, were originally based on specimens of a minute,
deep-water Atlantic limpet recovered from several stations
in the vicinity of the Azores on the remains of cephalopod
beaks. The type species, B. conicum Dautzenberg &
Fischer, 1901, was originally described as Lepeta costulata
Locard, 1898, and the type is thus a synonym of B. cos- _
tulatum.
The radula of the type species, as drawn by PELSENEER
(1901), who described the anatomy from material sup-
plied by Dautzenberg and Fischer, is clearly unusual in
form and difficult to interpret. Although PELSENEER con-
cluded that the species was a patellacean limpet, the rad-
ula is not docoglossan, nor can it be derived from a doco-
glossan form of dentition.
Minute limpets subsequently recovered from cephalo-
pod beaks in deep water in both the eastern and western
Pacific and depicted as having radulae of similar config-
Page 79
uration have been assigned not only to Bathysciadium
(DALL, 1908; THIELE, 1908) but also serve as type species
for the genera Bonus Moskalev, 1973, and Bathypelta
Moskalev, 1971. On the grounds that specimens have been
reported with and without gills and with one and two
kidneys, MosKALEV (1971) distinguished two families
(Bathysciadiidae and Bathypeltidae) and two superfami-
lies (Bathysciadoidea and Bathypeltoidea), both allied with
the docoglossan limpets (MOSKALEV, 1971, 1973, 1978).
The literature treating the anatomy of Bathysciadium
and its allies is written in four languages (English, French,
German, and Russian), and reconciliation of existing dif-
ferences of opinion is hampered not only by language dif-
ficulties but also by the fact that no one has yet been able
to compare the anatomy of specimens from the Atlantic
and Pacific.
The extraordinary radula of Bathysciadium pacificum
Dall, 1908 (Figure 9) does not fit any of the major radula
types described to date and is so highly modified that it is
not possible to determine the type of radula from which
it is derived. There is a broad central portion of radular
membrane that is without teeth. This region is flanked by
two elevated, lateral columns of heavy plates that are in-
terlocked or partially fused, both within rows and within
columns, to form continuous, flexible, jointed pavements.
A great deal of topographic relief is revealed in paired
stereomicrographs of the pavements (Figures 37a, b).
There are four plates in each half row: a small inner plate
that forms a steep inner wall and partially underlies the
adjacent plate; two larger, broadly rectangular plates that
are most elevated at the joint between them; and a small,
but heavy, outer plate that is squarish in outline, but with
a strong elevated ridge parallel to the column axis that
divides the plate into steeply-inclined inner and outer faces.
On the basis of the inferred striking similarity of rad-
ular configuration and ecological association with remains
of cephalopod beaks, it seems probable that the forms
described to date are very closely related and may not
merit taxonomic distinction of the magnitude proposed by
MosKALEV (1971, 1973). The radula is neither rhipido-
Explanation of Figures 9 to 17
Figure 9. Bathysciadium pacificum Dall, 1908. Los Angeles
County Museum of Natural History (LACM) 66-152. Bar =
100 um.
Figure 10. Addisonia paradoxa Dall, 1882. USNM 181201. Bar =
40 um.
Figure 11. Lepetella tubicola Verrill, 1881. USNM 153171. Bar =
40 um.
Figure 12. L. tubicola. Detail of newly forming rachidian teeth
from posterior end of same radula illustrated in Figure 11. Bar =
20 um.
Figure 13. Addisonia paradoxa. Enlargement of the outer two
heavily cusped radular plates from same radula illustrated in
Figure 10. Structure at arrow may be a degenerate marginal
tooth. Bar = 20 um.
Figure 14. Cocculina sp. A. Zoological Museum, University of
Copenhagen, Galathea Station 65. Bar = 40 um.
Figure 15. Cocculina sp. B. U.S. Fish and Wildlife Service Bu-
reau of Commercial Fisheries, R. N. Oregon II, Station 11220.
Bar = 40 um.
Figure 16. Cocculina sp. C. LACM, uncataloged. Bar = 100 um.
Figure 17. Cocculina sp. D. Zoological Museum, University of
Copenhagen, Galathea Station 276. Bar = 40 um.
No. 2
b)
The Veliger, Vol. 26
Page 80
C. S. Hickman, 1983
glossan nor docoglossan, and determination of the system-
atic position of the Bathysciadiidae and resolution of dis-
crepancies in the literature await careful examination and
comparison of the soft anatomy of the constituent species.
Although the substrate of these limpets is potentially
difficult to locate and colonize, it is now known that the
beaks of cephalopods may form extensive and dense, but
highly localized, accumulations at abyssal and hadal
depths. BELYAEV (1966) has estimated that they exceed
1000 per m? over extensive areas. Beaks that have been
occupied by bathysciadiid limpets are extensively pitted
and scarred. There is one species of cocculinid limpet that
also lives on cephalopod beaks in the lower abyssal zone,
described by MosKALEV (1976) as Teuthirostria cancellata.
Although cocculinids normally live on wood, the radula
of the cephalopod-beak species is typically cocculinid and
is in no way convergent with the bathysciadiid radula.
Addisoniid Limpets (Figures 10, 13, 38a, b)
The genus Addisonia Dall, 1882, includes small, deep-
sea limpets with thin, markedly asymmetrical shells and
a series of anatomical and radular peculiarities that war-
rant distinction as a separate family, as recognized by
DALL (1882). The anatomy is, however, incompletely de-
scribed (DALL, 1882; VERRILL, 1884; THIELE, 1908), and
requires further detailed study to clarify the affinities of
the family.
The radula (Figure 10), like that of bathysciadiids, con-
sists of a pavement of radular plates rather than distinctly
cusped teeth, although there is no relationship between
the plate patterns that would suggest any commonality of
descent. It is neither rhipidoglossan nor docoglossan in
form, unless one wishes to interpret the outermost element
(see arrow in Figure 13) as a degenerate rhipidoglossan
Page 81
marginal. The number of elements in each transverse row
is 15, as interpreted by MOSKALEV (1971, p. 59), although
the base number is not clear in the ambiguous series of
drawings in the literature (e.g., VERRILL, 1884, pl. 29, fig.
14; THIELE, 1908, pl. 1, fig. 9; DALL, 1889, pl. 25, fig.
le); and the shapes of individual elements cannot be de-
termined accurately from light microscopy because of their
minute size and overlap.
Stereographic-paired, scanning electron micrographs
(Figures 38a, b) clarify relationships in the addisoniid
radula. The rachidian is a well-developed, subcylindrical
element that fits together with the rachidian elements an-
terior to and posterior to it to form a continuous, jointed,
cylindrical column along the central longitudinal axis of
the radula. The rachidian is flanked on either side by a
pair of solid plates of rhomboidal outline, which are in
turn flanked by a pair of small, narrow plates of sigmoid
outline. The outermost elements in each half row are two
complexly interlocked and heavily cusped plates that are
elevated above the remainder of the radular ribbon and a
narrow, elongate element that may represent a degenerate
marginal tooth shaft. Nothing is known of the substrate
preference of the type species (Addisonia paradoxa Dall,
1882) but specimens of an Addisonia from the eastern
Pacific were extracted from inside of a skate egg case (J.
H. McLean, written communication, 1983).
Lepetellid Limpets (Figures 11, 12, 39a, b)
Another group of minute, deep-sea limpets with a
unique radular pattern and unique substrate association
is the family Lepetellidae Dall, 1882, typified by Lepetella
Verrill, 1880. The Atlantic type species, L. tubscola Ver-
rill, 1880, occurs consistently on and in the tubes of the
cosmopolitan polychaete genus Hyalinoecra Malmgren,
Explanation of Figures 18 to 27
Figure 18. Detail of rachidian tooth from cocculinid radula in
Figure 15. Note that the cusp is triangular and undivided. Bar =
10 um.
Figure 19. Detail of rachidian and left lateral teeth from coc-
culinid radula in Figure 14. Note that rachidian cusp is
5-pronged. Bar = 20 wm.
Figure 20. Cocculina sp. E. Australian Museum C.108570. Note
the great length and complex morphology of the massive outer
lateral tooth and the flattening of marginal tooth shafts. Bar =
40 um.
Figure 21. Enlargement of the surface of the cusp of the massive
cocculinacean outer lateral tooth illustrated in Figure 20, with
its unusual divaricate surface sculpture. Bar = 4 wm.
Figure 22. Enlargement of cocculinacean marginal tooth shafts
from the radula illustrated in Figure 15 and showing prominent
flexure at mid height. Bar = 10 um.
Figure 23. Fedikovella caymanensis Moskalev, 1976. Zoological
Museum, University of Copenhagen, ex Akademik Kurchatov
Station 1189. Bar = 40 um.
Figure 24. Pseudococculina sp. A. Zoological Museum, Univer-
sity of Copenhagen, ex Akademik Kurchatov Station 1267. Note
the particularly well-developed rachidian. Bar = 40 um.
Figure 25. Pseudococculina sp. B: Australian Museum 79-05-07.
The rachidian is a robust plate lacking the shaft seen in Figure
24. Note strong development of cusps on the large outer lateral.
Bar = 40 um.
Figure 26. Caymanabyssia spina Moskalev, 1976. Although poor-
ly developed, this is recognizable as pseudococculinid dentition.
Bar = 40 um.
Figure 27. Pseudococculina sp. C. Zoological Museum, Univer-
sity of Copenhagen, Galathea Station 664. Bar = 20 um.
Page 82
1867 (VERRILL, 1880; DALL, 1882, 1889; MOSKALEV,
1978). Minute limpets have also been removed from Hy-
alinoecia tubes from deep water off New Zealand. They
were originally described by SUTER (1908) as Cocculina
clypidellaeformis, but FINLAY (1927) subsequently desig-
nated this species as type species of the genus Tectiswmen.
Although the affinities of many monotypic, or allegedly
monotypic, austral gastropod genera have not been re-
solved, radular preparations from the type species of TJec-
tisumen Finlay, 1927, and Tecticrater Dell, 1956, have
revealed dentition of the same pattern as Lepetella tubicola.
Although VERRILL (1880) described the radula of Le-
petella tubicola as taenioglossate, this radula provides
another example of dentition that does not fit the standard
radular classification employing “glossate” terminology.
The positionally central tooth of L. tubscola (Figure 11)
is broad, with a pair of lateral cusps that may result from
fusion of once distinct lateral teeth. Fusion is suggested
by the pattern of ontogenetic development (Figure 12), in
which the earliest stage is the appearance of two cusps
separated by a space on the radular membrane. There are
three additional elements in the lepetellid radula: a small,
free-standing inner lateral tooth with a robust, curved,
and inward-pointed cusp, and a massive, tricusped outer
lateral that is closely articulated with a large marginal
plate. The marginal plates are of an unusual broad and
flattened form, and they interlock with one another as well
as with the bases of the massive outer laterals. Each plate
has four interactions: one each with the plates anterior
and posterior to it, and one each with the posterior and
anterior basal faces of adjacent outer lateral teeth. Paired
stereo-micrographs (Figures 39a, b) demonstrate that the
plates are not elevated pavements analogous to those of
Bathysciadium, Addisonia, or Laevinesta, and they are in-
ferred to function solely in mechanical adjustments of the
inner laterals rather than in food preparation and collec-
tion.
Cocculinid Limpets (Figures 14-23)
Cocculinid limpets are small-shelled (usually less than
5 mm maximum length) wood-ingesting gastropods with
minute radulae that have been difficult to evaluate with
light microscopy. Although two major genera are. tradi-
tionally assigned to the family (KNIGHT ef al., 1960;
MOSKALEV, 1971, 1976), Cocculina Dall, 1882, and Pseu-
dococculina Schepman, 1908, the radulae in these two gen-
era are of radically different plans that require the rec-
ognition of separate families (HICKMAN, in press).
The cocculinid radula has many features that make it
easy to recognize. Figures 14-17 illustrate a range of vari-
ation in this plan. The rachidian tooth ranges from well-
developed and cusped (Figure 14) to completely absent,
leaving a gap on the radular membrane (Figure 17). Like
many presence/absence characters, however, taxonomic
significance should not be attached to this. Note that in
Figure 15 these two character states exist along the length
The Veliger, Vol. 26, No. 2
of the same radula. Although the rachidian forms initially
in some species, it frequently is lost from the anterior half
of the membrane. When present, the rachidian consists of
two basal limbs that resemble the shafts of lateral teeth
that fuse medially to form a short shaft and cusp (Figure
18). The cusp may be entire and bluntly triangular (Fig-
ure 18) or subdivided into 3-5 secondary cusps (Figure
1D).
There are always three inner lateral teeth of similar
morphology (Figure 19), with long, slender shafts and
small, coarsely divided cusps. The robustness of the inner
lateral teeth is variable, but robust laterals are not posi-
tively correlated with the presence of a well-developed
rachidian, as illustrated in Figure 16. This radula is par-
ticularly interesting because there appear to be four well-
developed, lateral tooth shafts. The tops of the inner pair
of shafts in each row appear to be broken off, which could
be interpreted as failure to fuse and form a rachidian.
The largest and best developed tooth in the cocculinid
radula is the massive outer lateral (Figures 19, 20), with
a large primary cusp and a smaller secondary cusp on
either side. The surface of the primary cusp is not smooth,
but bears a unique pattern of divaricate wrinkles (Figure
21). These massive, major food-preparing teeth fold to-
gether in alternating zipper-like fashion when the radula
is enrolled during retraction at the end of the feeding
stroke and for storage within the radula sac (HICKMAN,
1981). Because of the size of the outer lateral tooth, the
cocculinid radula provides a classic example of lack of
coincidence of what HICKMAN (in press) calls “base rows”
and “cusp rows.” That is to say that the cusp of the outer
lateral is in a row of cusps that is different from the row
of bases, making for a much more complex form of func-
tional integration of tooth interactions than is possible in
the standard rhipidoglossan radula where base and cusp
rows coincide.
The marginal teeth in the cocculinid radula are also
unique. The innermost marginals have greatly expanded
and flattened shafts that narrow distally to disproportion-
ately tiny, but strongly hooked, cusps. The outer margin-
als retain this same basic form, with strong lateral flat-
tening of the shafts, but the shaft develops a peculiar twist
at mid-length (Figure 22) that is of a design that would
facilitate rotation in the upper shaft while the lower shaft
remains stationary. There also appears to be a tendency
for lower shafts to become fused below the twist. These
teeth are extraordinarily long, and like the massive outer
lateral, the cusp rows and base rows do not coincide.
MOosKALEV (1976) described six new cocculinid genera
based on abundant material collected from abyssal and
hadal depths on eight Soviet expeditions. Four of the gen-
era are based on species with pseudococculinid radulae,
and these will be discussed in the following section. The
other two, Fedikovella and Teuthirostria, have typical coc-
culinid radulae. I have examined the radula of Fedikovella
caymanensis from a specimen collected on the Akademik
Kurchatov Expedition (Figure 23) and do not feel that it
C. S. Hickman, 1983
is sufficiently different to warrant separate generic rec-
ognition. MOSKALEV based the new name on the triden-
ticulate condition of the rachidian, but, as discussed above,
the condition of the rachidian in cocculinids is more a
result of how faithfully the instructions are carried out in
forming the tooth rather than any major variation in the
nature of the instructions. Teuthirostria cancellata Mos-
kalev, 1976, from the Peru-Chile Trench, is an interesting
cocculinid because it occurs on squid beaks, along with
Bathysciadium, rather than on wood. There is, however,
no sign of any convergence on bathysciadiid radular mor-
phology.
DALL (1889) proposed Coccopygia for Cocculina spini-
gera Jeffreys, 1883, on the basis of the absence of epipo-
dial tentacles. Coccopygia is, however, a preoccupied name,
and the radula of C. spinigera is not distinct from that of
other species of Cocculina (based on SEM examination of
radulae from USNM 177890). Maoricrater Dell, 1956,
which has been placed in the Cocculinidae (KNIGHT et
al., 1960), has a docoglossan radula and belongs in the
Lepetidae. The animal and radula of Notocrater Finlay,
1927, are not known, and it too may be a lepetid.
Detailed studies of the anatomy of the cocculinids are
badly needed in order to establish the systematic position
of these minute rhipidoglossan limpets and their relation-
ships to other deep-sea families. The only account of the
internal anatomy of a cocculinid is that of THIELE (1903),
who concluded that their closest affinities were with the
Neritacea.
Shell morphology of the cocculinids likewise stands in
need of review. Although the apex of the shell is poste-
riorly directed in all species, it varies in placement from
far posterior to central; and the shell may be tall and
narrowly conical or extremely flattened. Shell surfaces vary
from smooth to highly ornamented and pustulose. How-
ever, shell surfaces are frequently badly corroded when
they reach the surface; and specimens that have been kept
in formalin or alcohol for long periods seem to be partic-
ularly susceptible to disintegration. Shells are best pre-
served dry, after being separated from animals that are to
be preserved wet. Occasionally, fresh specimens preserve
extraordinarily elaborate spinose periostracum (Lipps &
HICKMAN, 1982, fig. 14-13).
Pseudococculinid Limpets (Figures 24-28, 40a, b)
Pseudococculinidae fam. nov.: Pseudococculina and a
group of allied small deep-sea limpets share a plan of
radular morphology that is so distinct from that of the
Cocculinidae as to warrant separate familial recognition.
The details of this plan are described below. The mor-
phological differences require fundamentally different
patterns of movement and mechanical interactions of teeth
within and between rows that are discussed elsewhere
(HICKMAN, in press).
Pseudococculinid limpets also occur on wood, and have
Page 83
shells and animals that are similar to cocculinid limpets.
SCHEPMAN (1908) proposed the genus Pseudococculina on
the basis of the unique radula of P. rugosplicata and P.
granulata. Although SCHEPMAN (p. 16) noted the presence
of a “plumate gill” in the type species, it is absent or
poorly developed in pseudococculinids I have examined.
As noted earlier, presence or absence of well-developed
respiratory organs does not seem to be of profound taxo-
nomic significance in deep-sea limpets, although the na-
ture of the respiratory structures, when present, can be
diagnostic. There are no published accounts of the inter-
nal anatomy of Pseudococculina, and detailed histological
comparisons with other deep-sea limpets will be required
in order to establish relationships.
The pseudococculinid radula is, like the cocculinid rad-
ula, so small that light microscopy has not been adequate
to diagnose it. It is superficially similar to the cocculinid
radula in the parallel trends toward degeneration of teeth
in the central field (particularly the rachidian) and the
elaboration of the outer lateral tooth as the major food-
preparing structure, accompanied by the development of
radular asymmetry.
Figures 24-26 illustrate a range of variation in pseu-
dococculinid radular morphology. The rachidian varies
from an asymmetric element with a prominent horseshoe-
shaped base and thinner, irregular, tapered extension that
cannot be differentiated into shaft and cusp (Figure 24)
to a thin, squarish or oval plate (Figure 26). The inter-
mediate condition (Figure 25) frequently involves the de-
velopment of a plate with thickened edges and irregular
or ragged edges or extensions. The degree of development
of the rachidian may vary along the length of a single
radula, as illustrated in Figure 27.
In contrast to the cocculinid condition, there are four,
rather than three, inner lateral teeth in the pseudococcu-
linid radula. The innermost lateral (Figure 27) is an un-
usual, large, triangular element with a long, inner basal
limb and shorter, outer basal limb that fits into a curved
pocket on the small second lateral. Figure 27 also illus-
trates the strongly asymmetric placement of these large
teeth on either side of the rachidian. The second, third,
and fourth laterals are all strongly curved elements that
have small, simple, distal cusps and are designed to inter-
lock closely when the radula is tightly enrolled. The outer
lateral (fifth lateral) is a massive tooth with a thickened
quadrate shaft with a deep pocket on the inner surface
that fits over the smaller inner lateral teeth when the
radula is not in use. The massive cusp is subdivided into
four blunt, terminal denticles. Unlike the massive outer
lateral in Cocculina, it is a short tooth, and its base and
cusp coincide with the bases and cusps of adjacent inner
lateral teeth.
The marginal teeth (Figure 28) have short, thick shafts
in contrast to the extreme flattening of the elongate and
twisted shafts of cocculinid marginals. The shaft thick-
ening is most pronounced in the inner four or five mar-
ginals, which also have long, curved, and sharply pointed
The Veliger, Vol. 26, No. 2
Page 84
C. S. Hickman, 1983
cusps. Outer marginals do, however, develop flattened
shafts, and the cusps are complexly serrate.
A stereographic pair of the pseudococculinid radula
(Figures 40a, b) demonstrates the extreme difference in
topography between the massive outer lateral and mar-
ginal complex and the poorly-developed central field of
teeth.
Moska.LeEv (1976) described four genera that I believe
to be simple variations on the basic pseudococculinid plan:
Kurilabyssia, Caymanabyssia, Bandabyssia, and Tentaocu-
lus. MOSKALEV’s drawings of the radulae (fig. 1, p. 10)
do indicate differences, but the differences seen in light
microscopic observations and drawings have to do with
degree of development rather than fundamental differ-
ences in plan. The radula of Caymanabyssia spina (Figure
20) represents the extreme case of not only an underde-
velopment of the plate-like rachidian, but also failure to |
develop the inner lateral tooth except in outline and slight
thickening.
MOsKALEV (1976) notes that Tentaoculus perlucida has
eyes, a feature that is lacking in other pseudococculinids
as well as cocculinids, addisoniids, and bathysciadiids. It
may be that there will be suites of anatomical differences
in many of the deep-sea limpet families that will justify
separate generic categories.
Pseudococculina is sometimes extremely abundant on
pieces of wood. MOSKALEV (1976) recovered 204 speci-
mens of Caymanabyssia spina from a piece of wood 800
mm X 150 mm in size, and large numbers of an unde-
scribed species of Pseudococculina have been recovered from
wood from deep-sea samples off the east coast of Australia
(personal observation).
Bathyphytophilid Limpets
Wood is not the only form of plant material that reaches
the deep sea floor in large quantities. There has been a
Page 85
great deal of interest in recent years in the export of or-
ganic matter from high productivity sea-grass beds along
the continental margins; and it has been established that
this material is transported by turbidity flows and accu-
mulates in deep-sea trenches. It is particularly abundant
in the Puerto Rico and Cayman Trenches, where blades
and rhizomes of Thalassia testudinum comprise 80-90% of
the plant material (MENZIES et al., 1967; MENZIES &
Rowe, 1969; WoLFF, 1976, 1979, 1980; GEORGE & HIG-
GINS, 1979). It is, therefore, not extraordinary that there
should be communities of deep-sea organisms specialized
for using sea grasses as a food source. MOSKALEV (1978)
based the family Bathyphytophilidae on a species of lim-
pet that inhabits Thalassia rhizomes in the Cayman
Trench. WOLFF (1979, 1980) who examined the Soviet
R/V Akademik Kurchatov material that formed the basis
for MOSKALEV’s description, observed that the limpets not
only occupy burrows in the rhizomes created by boring
bivalves, but that they may also occur in their own feeding
cavities within the pithy center of the rhizome.
The bathyphytophilid shell has a cocculinacean ap-
pearance, minute and with a posterior-directed apex, but
the radula is distinct from all other minute abyssal limpet
groups. I have not been able to obtain material of the
Thalassia-inhabiting limpets, but MOSKALEV’S illustration
clearly indicates that it is a rhipidoglossan radula with
extreme reduction in the number of marginal teeth to 5-
20. There are ambiguities in the drawings, but the most
striking feature is the narrowness of the central field, where
there is a single (poorly-developed?) rachidian, and the
two massive (?) overlapping major lateral elements, which
are at least superficially similar to the large overlapping
elements of the addisoniid radula. The radula is strongly
asymmetric. In addition to the type species, Bathyphytoph-
ilus caribaeus, MOSKALEV (1978) described Aenigmabonus
kurilokamtschaticus from the Kurile-Kamchatka Trench,
but the substrate association of the second species is not
known.
Explanation of Figures 28 to 36
Figure 28. Detail of marginal tooth complex from radula illus-
trated in Figure 27. Note differentiation of five inner marginals
with unusually large shafts and cusps. Bar = 20 um.
Figure 29. Choristella n. sp. LACM 77-374. Bar = 40 um.
Figure 30. Neomphalus fretterae McLean, 1981. Deep-sea Re-
search Vessel (DSRV) Alvin Dive 733. Bar = 100 um.
Figure 31. Newly formed rachidian and left inner lateral teeth
of N. fretterae from posterior end of radula. Bar = 40 um.
Figure 32. Worn rachidian and left inner lateral teeth of N.
fretterae from same radula illustrated in Figure 31. Bar = 40 wm.
Figure 33. Radula of an undescribed deep-sea hydrothermal vent
limpet, illustrating a rhipidoglossan plan shared by five new vent
species. DSRV Alvin Dive 982. Bar = 40 um.
Figure 34. Radula of an undescribed deep-sea hydrothermal vent
limpet illustrating a new rhipidoglossan plan shared by four
undescribed species. DSRV Alvin Dive 880. Bar = 100 um.
Figure 35. Radula of an undescribed hydrothermal vent limpet
illustrating a new radular pattern not falling under standard
classification and shared by two new species. DSRV Alvin Dive
879. Bar = 20 pm.
Figure 36. Radula of a second specimen of the limpet illustrated
in Figure 35. Note that the dentition from a comparable portion
of the radula is poorly developed, with cusps lacking on the
rachidian and laterals. DSRV Alvin Dive 879. Bar = 20 um.
Page 86
Cocculinellid Limpets and Choristellids
(Figure 29)
THIELE (1909) proposed the genus Cocculinella for a
minute, deep-sea limpet with a unique non-rhipidoglos-
san radular pattern in which the rachidian is unusually
small and narrow, with five heavier teeth on either side.
THIELE’S drawing of a half row of the radula (THIELE,
1909, pl. 1, fig. 8) and his description (pp. 21-22) indicate
that the best-developed tooth is the bicuspid second lateral,
and that the three outer laterals are of similar morphology
but decreasing size. THIELE placed the genus with Lepe-
tella in the Lepetellidae, with the interpretation that the
large outer plate in the radula of Lepetella may be thought
of as a fusion of the three outer laterals of Cocculinella.
Unfortunately, no subsequent collections of animals of
Cocculinella minutissima (Smith, 1904) are available for
study. However, the radula of a minute, coiled deep-sea
gastropod that is commonly associated with unusual sub-
strates shows the same basic pattern (Figure 29). These
coiled gastropods have been placed in the genus Chorvstella
Bush, 1897 (Choristes auctt., non Carpenter, 1872). The
radula has never been well understood, and there is a
great deal of variation in the three drawings that have
been published for the Atlantic species (VERRILL, 1882;
BusH, 1897; BOUCHET & WarEN, 1979). The ambigui-
ties, however, are reconciled by the scanning electron mi-
crograph of an undescribed species (J. H. McLean, in
preparation) from the Eastern Pacific (Figure 29). Ponder
(unpublished) has scanned the radula of an undescribed
species from off the Queensland coast, and it is compa-
rable in numerous details (personal observation).
Although substrate data are not available in most in-
stances, where known, choristellids occur on or in the egg
cases of sharks (KURODA e¢ al., 1971) or skates (VERRILL,
1884).
The radular evidence for close affinities of a limpet and
a coiled, operculate gastropod poses problems of classifi-
cation that cannot be resolved within the scope of this
paper and without reference to anatomy. Separate familial
names are available: MOSKALEV (1971) proposed the Coc-
culinellidae, placing it in the Lepetelloidea, and BOUCHET
& WAREN (1979) have justified the change of the familial
name Choristidae to Choristellidae. KURODA e¢ al. (1971)
proposed the Choristiacea (=Choristelliacea) as a super-
family, making this name available for hierarchically. re-
lating these two families of disparate shell morphology.
Hydrothermal Vent Limpets (Figures 30-36)
The remaining four groups of deep-sea limpets are all
associated with unconventional substrates and food sources
at abyssal hydrothermal vents that have developed at di-
vergent oceanic plate boundaries. The animals themselves
occur on basalt surfaces, on polymetallic sulfide mounds
and chimneys, or on the surfaces of sessile vent organisms
such as the giant vestimentiferan worms or mussels. Che-
mosynthetic bacteria, which are the only known primary
The Veliger, Vol. 26, No. 2
producers in the deep sea, form the base of the unique
food chain in this environment (JANNASCH & WIRSEN,
1979, 1981; Rau & HEDGES, 1979; Karu et al., 1980;
CAVANAUGH et al., 1981; Rau, 1981). They are consumed
directly by many of the vent organisms, which may either
scrape bacterial films from hard substrata or filter bacteria
that are suspended abundantly in the water column. Of
the extraordinary diversity of limpets that have been re-
covered to date from vent communities, only one species,
Neomphalus fretterae, has been described (MCLEAN, 1981).
Nine additional limpets remain to be described
(McLean, in progress) as well as a secondarily flattened
operculate species that is closely related to one of the lim-
pet groups. McLean (written communication, 1982) ten-
tatively recognizes three new families among the remain-
ing 10 species. I have prepared and examined radulae of
all the species and find three corresponding new radula
types. Scanning electron micrographs are presented for
each of the major radula patterns to facilitate comparison
with patterns in deep-sea limpets from other environmen-
tal settings. Detailed descriptions of these radulae will be
published as an adjunct to the descriptions of the new
taxa (Hickman, in preparation).
Neomphalid limpets: One of the most abundant limpets
at hydrothermal vents, particularly along the Galapagos
Fracture Zone, is Neomphalus fretterae, a gastropod of
such distinctive anatomy and shell morphology as to re-
quire separate familial and superfamilial status (Mc-
LEAN, 1981; FRETTER ef al., 1981). As illustrated in Fig-
ure 30, it is rhipidoglossan in form, and the most
remarkable feature is the robust development of the den-
tition, with no indication of degeneration of teeth in the
central field. The rachidian and five laterals are not only
supplied with prominent pointed cusps, but the shafts are
heavily reinforced, as are the complexly interlocking bas-
es. The robust development is all the more remarkable in
view of the enlarged mantle cavity and ctenidium and
accompanying modifications for suspension feeding.
Although the animals seem to be sedentary, conforming
in shell growth to irregularities in the substrate at their
home sites, they may derive a significant proportion of
their nutrition from the bacterial films that develop on the
basalt. FRETTER et al. (1981) note larger particles in the
fecal string, suggesting a mixed feeding strategy. It is clear
from comparison of micrographs of newly formed teeth
and teeth from the working portion of the same radula
(Figures 31, 32) that the teeth are used and sustain sub-
stantial abrasion. The marginal teeth are delicate and finely
serrate, frequently showing complex patterns of incom-
plete separation of teeth during ontogeny and irregulari-
ties that suggest lack of strong selection for normal devel-
opment (HICKMAN, 1980, p. 292, fig. 6c).
Hydrothermal vent Group-A limpets: Five hydrothermal vent
gastropods share the rhipidoglossan radular pattern illus-
trated in Figure 33. The shell morphology within this
group is diverse and ranges from a minute, conispirally
Crs rickman 1983
coiled, operculate species (Hickman, MS) to flattened
forms that properly may be called limpets. The animals
have numerous features indicating that their closest rela-
tives are trochacean gastropods. I have tentatively placed
the coiled species in the Trochacea, although anatomical
evidence may lend support to establishment of a separate
superfamily within the suborder Trochina. Vera Fretter
is currently studying the anatomy of the limpet members
of this group.
In spite of the broad range of shell form, the radula is
remarkably constant in morphology throughout the group.
It is similar to the trochacean radular plan in the small
base number of well-developed teeth in the central field
and in the pattern of shaft reinforcement and within-row
basal interlock. It is a relatively narrow radula, in part
because the marginal tooth rows, although long, are set at
a very low angle to the longitudinal axis of the ribbon.
One of the most striking features of the radula is the wide
spacing between rows in the central field, with tooth bases
completely exposed. The wide spacing is correlated with
an alternation in the position of the ends of lateral tooth
rows and the beginnings of marginal tooth rows. A similar
kind of accommodational alternation occurs in the neri-
tacean radula (HICKMAN, in press).
The substrate preferences and food sources of members
of this group are not well understood. Three of the five
species occur at high-temperature vents on the East Pacific
Rise, where they have been removed from polymetallic
sulfide build-ups surrounding the high-temperature ef-
fluents. At these high-temperature vents, where water may
be emitted at temperatures in excess of 350°C (in contrast
to some of the ‘“‘warm” vents in the Galapagos that do not
exceed 22°C), there are many fewer animals. Members of
this limpet group also have been recovered from washings
of the giant tube worm Riftia, and there may be significant
microhabitat specialization within the complex.
Hydrothermal vent Group-B limpets: Four limpet
species share the basic radular pattern illustrated in Fig-
ure 34. These species also share a combination of anatom-
ical features that is unique to the Gastropoda (McLean,
written communications, 1982-1983). Fretter is currently
studying the anatomy of these limpets as well. The radula
is rhipidoglossan, and as in the other rhipidoglossan vent
limpet groups, the rachidian and lateral teeth are very
well developed. The rachidian is a relatively small element
with a sturdy basal support for the sharply pointed and
finely denticulate cusp. The most unusual element in the
radula is the inner lateral tooth with its massive, com-
plexly divided, and finely denticulate compound cusp and
broadened shaft. The cusp is oriented on a strong diagonal
to the longitudinal axis of the radula, connecting the ra-
chidian cusp with the four outer lateral cusps that are
situated considerably anterior to the rachidian. This ar-
rangement produces a strong, posteriorly directed dip in
the cusp row. The shafts of the four outer laterals all have
Page 87
a characteristic sharp bend at mid height that accommo-
dates the cusps of the next row posterior. Shafts also have
lateral expansions to facilitate within-row interlock. The
marginal teeth are numerous, with flattened shafts and
finely denticulate cusps.
Hydrothermal vent Group-C limpets: Two of the lim-
pet species collected to date from deep-sea hydrothermal
vents have the non-rhipidoglossan radular plan illustrated
in Figure 36. Like the radulae of bathysciadiids, addisoni-
ids, and lepetellids, it does not fit into the standard clas-
sification of radula types. The bases, shafts, and cusps of
the five radular elements are unique in form. The single
most unusual feature of the radula is the interaction be-
tween the base of the second lateral and the cusp of the
third lateral of the same row. Within-row interactions in
other radulae are cusp-cusp or base-base, but in this group
there is a prominent basal projection or fold on the second
lateral that fits or locks beneath the cusp of the adjacent
third lateral.
The rachidian is a small tooth with a pointed triangular
cusp. Its base is a short transverse bar that fits into deep
pockets on the bases of the inner lateral teeth. The three
inner laterals are of similar general form with thin, rel-
atively broad and flexuous cusps, complex sinuous shafts,
and interlocking basal folds. The outer lateral is a broad,
flattened, spoon-shaped element with a semicircular rim
of folded-over or enrolled chitin that is perhaps best not
termed a cusp.
The entire radula is very small and insubstantial, and
in one specimen that I have prepared (Figure 36) failure
of normal cusps to develop suggests that selection pressure
to reproduce faithfully the standard plan is not great.
DISCUSSION
Radular Characters and Systematics
Sixteen distinct deep-sea radular patterns are illustrat-
ed in this paper. Although two of them are docoglossan
and nine are rhipidoglossan, five do not fit the standard
classification scheme. Even the docoglossan and rhipido-
glossan radulae have patterns that are distinct in many
details from those of related shallow-water groups, and in
some cases deep-water families cannot be related to extant
shallow-water families or to one another on radular char-
acters. Some discussion of the role of radular characters
in further systematic evaluation of deep-sea limpets is in
order.
Although a primary purpose of this paper is to provide
data for dealing with the systematics and classification of
deep-sea limpets, the radular data are biased toward an
emphasis of differences rather than similarities. Radular
characters will continue to be important in dealing with
these taxa, but they will be most valuable in differentiat-
ing genera and species within families. The major pat-
terns are too distinct from one another and from patterns
Page 88 The Veliger, Vol. 26, No.
C. S. Hickman, 1983
in other gastropod groups to provide reliable data for es-
tablishing higher relationships.
This leaves us with something of a dilemma as to where
to seek shared characters that will enable us to place many
of these taxa into phylogenetic perspective. The shells are
extraordinarily similar, but in shell form we are dealing
with strong evolutionary convergence. Shell microstruc-
ture may prove useful, although the emphasis should be
on details of the mineral species and fabrics that are pres-
ent rather than on absences that may be due to a secondary
simplification of structure. Loss of shell layers, particu-
larly the inner nacreous layer, appears to be strongly cor-
related with small size (Hickman, MS), and therefore
should not be heavily weighted in taxonomy. The most
reliable clues should be revealed through detailed com-
parative anatomical studies. Here too, however, it must
be remembered that the limpet grade of evolution requires
modifications of anatomical blueprints that were accom-
modated to life in a coiled shell. Detailed comparative
histological analyses are a formidable task, but will prob-
ably be necessary because gross anatomical features are
inadequate to establish relationships.
Ecological and Evolutionary Implications
What we now know about the radular morphology,
habitats, and substrates of deep-sea limpets has some im-
portant evolutionary and ecological implications. It has
long been held that feeding structures in organisms are
easily modified in relationship to substrates and food pref-
erences and, thus, are not likely to provide good characters
for differentiating taxa (see HOUBRICK, 1978, and refer-
ences therein). Although this may be the case in some
groups of gastropods, it is not a generalization that can be
extended to the entire class (HICKMAN, 1980, 1982). This
is nowhere better demonstrated than in the taxa of deep-
sea limpets that have converged on feeding on unconven-
tional substrates. For example, cocculinid limpets re-
covered from wood have the same radular pattern as the
cocculinid limpet recovered from squid beaks. Bathyscia-
diid limpets from squid beaks have a radular pattern that
shows no convergence with the cocculinid squid-beak
species. Likewise, wood-ingesting docoglossans, wood-in-
gesting cocculinids, and wood-ingesting pseudococculinids
retain highly distinctive dentition patterns. In each of these
three groups, there are formidable, major food-preparing
Page 89
teeth that we may infer to be adequate designs for dealing
with water-logged wood. However, it would be difficult
to argue that any one of these solutions is an optimal one.
Many evolutionary biologists and ecologists have based
their research on the assumption that evolution involves a
great deal of fine-tuning and optimization; but ideal so-
lutions may be prohibitively costly to produce and main-
tain, and many organisms may be built simply to “get by”
(CowEN, 1981; HICKMAN, 1982). Limpets in the deep sea
seem to have developed a number of alternative solutions
to feeding on a number of difficult or unusual substrates.
What is peculiar is the strong convergence in shell shape.
It is not at all clear what the advantages of secondary
flattening are to so many forms that colonize unconven-
tional substrates in the deep sea. It is certain that the
limpet shell form does not have the same protective func-
tions in small deep-sea limpets that it does in shallow-
water limpets.
Connections Between Cambrian Limpets and
Deep-Sea Limpets
This brings us again to the question of size and the
proposition in the introduction that there may be some
connection between the predominance of small cap-shaped
shells in the early evolution of the Mollusca and the pleth-
ora of such forms in the deep sea today. If we accept the
proposition that the protective mechanical functions of shell
form that work in large shallow-water limpets do not
apply to minute deep-sea limpets or to the Cambrian early
mollusk radiations, what similarities do these forms share
that might suggest alternative hypotheses?
Although VERMEIJ (1971, 1973) has correctly empha-
sized the increase in the morphological diversity of gas-
tropod shells as a result of increase in the number of pa-
rameters controlling shell geometry, it does not follow that
more complex shell geometry permits greater diversity of
anatomical organization. The simple geometric form of
the limpet permits an extraordinary variation in anatom-
ical organization.
Lindberg and Wright (in MS) have shown that shell
shape can place interesting volumetric constraints on the
ways that anatomical plans can be varied with respect to
reproductive modes and that some modes are more likely
in limpets. Another important constraint, I believe, is that
on respiration. The uncoiled limpet shape, especially when
Explanation of Figures 37 to 40
Paired stereo micrographs illustrating topographic differences in
four deep- sea limpet radular groundplans.
Figure 37. Bathysciadium pacificum (same radula illustrated in
Figure 9). Bar = 50 um.
Figure 38. Addisonia n. sp. LACM, uncataloged. Bar = 50 wm.
Figure 39. Lepetella tubicola (radula illustrated in Figure 11).
Bar = 20 um.
Figure 40. Pseudococculina sp. C (radula illustrated in Figure
27). Bar = 40 um.
Page 90
coupled with small size, provides a great deal of versatility
in modes of respiration. Discrete respiratory organs are
not essential in small flat animals. And even when present,
such organs do not require active control of water cur-
rents. Although much has been made of the position of
the “mantle cavity” in the interpretation and classification
of early mollusks, the concept of the cavity needs critical
reexamination.
The concept derives in part from the standard drawings
and discussions of the Hypothetical Ancestral Mollusk
(YONGE & THOMPSON, 1976). A number of authors have
advised of the dangers in using HAM to understand mol-
luscan evolution (e.g., MORTON, 1967; STASEK, 1972;
PojJETA, 1980), but many of the implications of the con-
cept have been perpetuated by its harshest critics. A man-
tle cavity need not be present at all. In flat, uncoiled mono-
placophoran limpets the respiratory structures are situated
in a pair of pallial grooves, not in a cavity. The notion
that the development of a dorsal calcified covering created
a mantle cavity is an oversimplification, and the conclu-
sion that it necessitated the development of gills (POJETA,
1980) is unwarranted.
The development of a distinct mantle cavity as opposed
to grooves, and increasingly efficient gill structures and
methods of passing water currents over them, are major
themes in gastropod evolution and have undoubtedly per-
mitted them to become large and active animals.
It is significant to note, however, that, in animals with
the limpet form, we can find everything from no discrete
respiratory organs at all to animals with true molluscan
ctenidia. And, in between, we can find animals with both
ctenidia and secondary gills and animals with secondary
gills but no ctenidia. We also see a range in the numbers
of these structures and the way that they are housed.
Modern limpets are much more adventuresome with res-
piration than are coiled gastropods, and there is some good
reason to believe that experimentation with respiration
was important in Cambrian mollusks. This is suggested,
for example, by the development of tubular structures
(RUNNEGAR & POJETA, 1974; RUNNEGAR & JELL, 1976)
in a number of tall cone-shaped, but minute, Cambrian
shells.
It must be remembered that modern deep-sea limpets
are not living fossil holdovers from the Cambrian: There
is too much evidence for secondary derivation from coiled
ancestors. But, keeping this fact in mind, the living minute
deep-sea limpets provide a wealth of anatomical infor-
mation about the possibilities for organization and exper-
imentation in the context of limpet geometry on a small
scale.
ACKNOWLEDGMENTS
I thank the following persons and institutions for assis-
tance in locating and borrowing specimens of deep-sea
limpets upon which this work is based: Torben Wolff and
Jorgen Knudsen (Zoological Museum, University of Co-
The Veliger, Vol. 26, No. 2
penhagen), Ruth Turner (Harvard University), Anders
Warén (University of Gothenberg), Eve Southward (Ma-
rine Biological Association of the United Kingdom), James
McLean (Los Angeles County Museum of Natural His-
tory), Winston Ponder and Phillip Colman (The Austra-
lian Museum), Joe Houbrick and Joe Rosewater (U.S.
National Museum of Natural History), Paula Mikkelsen
(Smithsonian Institution Fort Pierce Bureau), K. D. Spring
(Continental Shelf Associates, Inc.), and the (U.S.) Bu-
reau of Land Management.
David Lindberg, James McLean and Winston Ponder
provided helpful criticism and suggestions for improve-
ment of the paper. I am particularly grateful to David
Lindberg for his advice on interpretation of docoglossan
radulae and for stimulating debates over the interpretation
of limpet anatomy and morphology. Scanning electron mi-
crographs were taken by the author in the Department of
Anatomy, University of California, San Francisco; and
the assistance of John Long and Jerry Morgan is grate-
fully acknowledged. I thank George Shkurkin for English
translations of the important Russian papers by Moska-
lev. Copies of these translations are in the Earth Sciences
Library, University of California. James Hickman as-
sisted in preparation of the final draft and with intercon-
tinental communications. The expeditions that have pro-
vided limpet material from deep-sea hydrothermal vents
have been supported by generous grants from the U.S.
National Science Foundation, and my research on gastro-
pod radulae by NSF grants DEB 77-14519 and DEB 80-
20992. Finally, I thank the Department of Malacology of
The Australian Museum for the numerous courtesies ex-
tended during the sabbatical leave that enabled completion
of this project.
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sea. In: R. C. Phillips & C. P. McRoy (eds.), Handbook of
seagrass biology: an ecosystem perspective. Garland STPM
Press, New York. pp. 199-224.
YONGE, C. M. 1960. Mantle cavity, habits, and habitat in the
blind limpet, Lepeta concentrica Middendorff. Proc. Calif.
Acad. Sci. (4th Ser.) 31(4):103-110.
YONGE, C. M. & T. E. THomMpson. 1976. Living marine mol-
luscs. William Collins Sons & Co., Ltd., London. 288 pp.
NOTE ADDED IN PROOF
A paper has just appeared in which B. A. MARSHALL
(1983. The family Cocculinellidae (Mollusca: Gastropo-
da) in New Zealand. Nat. Mus. New Zealand, Records
2(12):139-143) provides new evidence on the biology and
morphology of Cocculinella. It fails to support the rela-
tionship with the Choristellidae proposed herein. The
radula of a new shallow-water (13 m) New Zealand species
is of a plan distinct from all the patterns illustrated in this
paper, and the specimens were removed from fish bone.
Marshall also reexamined syntypes of the type species and
discovered that they were on fish bone, not on ‘water-
logged wood’ as stated in the original description.
The Veliger 26(2):93-95 (October 3, 1983)
THE VELIGER
© CMS, Inc., 1983
Additions to the Opisthobranch Mollusk Fauna of
Marin County, California, with Notes on the
Biology of Certain Species
WILLIAM B. JAECKLE
Department of Biological Sciences, University of Southern California,
University Park, Los Angeles, California 90089
Abstract. Seven species of opisthobranch Mollusca from Marin County, California are discussed,
and certain aspects of their biology presented. Three species are new additions to the faunistic list of
this area; one sighting represents a geographical range extension.
THE OPISTHOBRANCH mollusks of Marin County, Cali-
fornia have been extensively documented in numerous re-
ports (STEINBERG, 1960, 1963; Marcus, 1961, 1964;
GOSLINER, 1968; GOSLINER & WILLIAMS, 1970, 1973;
WILLIAMS, 1971; GODDARD, 1973; BEHRENS, 1980b;
JAECKLE, 1981) in which a total of 74 species have been
reported. Since 1977, this aspect of the littoral invertebrate
fauna has been intermittently examined, and several
species, previously unreported from this area, have been
observed. These observations, as well as aspects of the
biology of certain species found in Marin County are re-
ported here. Species not previously reported from Marin
County are denoted by an *; extension of the geographical
range is denoted by a **.
Systematic List of Discussed Species
Subclass Opisthobranchia
Order Nudibranchia
Suborder Doridacea
Family Cadlinidae
Cadlina sparsa (Odhner, 1921)**
Family Aldisidae
Aldisa sanguinea (Cooper, 1863)*
Suborder Dendronotacea
Family Dotidae
Doto kya Marcus, 1961
Suborder Arminacea
Family Janolidae
Janolus barbarensis (Cooper, 1863)*
Janolus fuscus O’ Donoghue, 1924
Suborder Aeolidacea
Family Flabellinidae
Flabellina trilineata (O’ Donoghue, 1921)
Family Tergipedidae
Tenellia adspera (Nordmann, 1845)*
Cadlina sparsa (Odhner, 1921)
Two specimens of this eudoridoidean species were col-
lected in a rocky, semi-protected littoral locality, the Fron-
tier Arts Nature Reserve (latitude 37°52’22”N; longitude
122°36'56”W). These collections represent a geographical
range extension, as well as an addition to the opistho-
branch fauna of Marin County. The previous northern-
most occurrence of Cadlina sparsa was Monterey Bay,
Monterey County, California (BEHRENS, 1980a). The col-
oration of these specimens differed from previously pub-
lished accounts. Typically, the rhinophores are light yel-
low to yellowish-brown in coloration (MCDONALD, 1977);
however, the rhinophoral coloration of the collected spec-
imens was light brown with numerous black spots on the
rhinophoral lamellae. A voucher specimen has been de-
posited in the invertebrate collection of the California
Academy of Sciences bearing the voucher number
CASIBP 030954.
Aldisa sanguinea (Cooper, 1863)
Although the geographical range of Aldisa sanguinea
extends from Coos Bay, Oregon to San Diego, California
and in the Gulf of California, Mexico (BERTSCH &
Page 94
JOHNSON, 1982), this species has not been reported from
Marin County. This species has been sighted in two rocky
littoral areas, Muir Beach Overlook (latitude 37°52'21”"N;
longitude 122°36'56”W) and the Frontier Arts Nature
Reserve.
Doto kya Marcus, 1961
This dendronotacean species is common in rocky litto-
ral and estuarine habitats of Marin County. Despite the
abundance of Doto kya in central California, the biology
of this species is poorly known. In rocky littoral habitats
of Marin County, specimens of D. kya have been observed
preying upon the leptomedusan hydrozoan Obelia dichoto-
ma (Linnaeus, 1758) and the anthomedusan species Sarsia
sp. Doto kya, in estuarine areas of San Francisco Bay,
feeds on O. dichotoma. The spawn masses of D. kya, de-
posited on the hydrocauli of O. dichotoma colonies, have
been found in both habitats.
Janolus barbarensis (Cooper, 1863)*
Janolus fuscus O’ Donoghue, 1924
GOSLINER (1981, 1982) synonymized the genus Antio-
pella Hoyle, 1902, with Janolus Bergh, 1884, and rein-
stated /. fuscus as a distinct species. Janolus barbarensis
and /. fuscus have been viewed as a single species for 15
years (GOSLINER, 1982) and, as a result, the geographical
ranges of both species have been combined by most au-
thors. GOSLINER (1982) mentioned this range overlap but
did not indicate their limits. In Marin County, /. barbar-
ensis has been found on wharf pilings at Sausalito, San
Francisco Bay (latitude 37°47'N; longitude 122°21’W) and
J. fuscus has been collected at Muir Beach Overlook and
the Frontier Arts Nature Reserve.
Flabellina trilineata (O’ Donoghue, 1921)
GOSLINER & GRIFFITHS (1981) synonymized the genus
Coryphella Gray, 1850, with Flabellina Voigt, 1834, due
to a lack of genus-specific morphological characters. In
Marin County, Flabellina trilineata occurs in both estua-
rine and marine habitats. At the Muir Beach Overlook
study site, this species was observed feeding on the antho-
medusan hydroid species Tubularia marina (Torrey, 1902)
and Sarsia sp. The specimens of F. trilineata selectively
preyed upon the tentacles of 7. marina, leaving the re-
maining portion of the polyp intact. This feeding selectiv-
ity differs from COOPER’s (1980) report that F. trilineata
consumes the entire polyp of Tubularia crocea (Agassiz,
1862) in Elkhorn Slough, Monterey County, California.
Tenellia adspera (Nordmann, 1845)*
Large numbers of Tenellia adspera have been observed
on wharf pilings in Sausalito, San Francisco Bay, feeding
on Obelia dichotoma during May—August, 1982. Although
T. adspera has been previously reported from San Fran-
The Veliger, Vol. 26, No. 2
cisco Bay (STEINBERG, 1960, 1963; BEHRENS, 1980b), this
is the first reported sighting from Marin County. The
examined specimens were small (<5 mm in length) and
exhibited a wide variation in the amount of black pigment
spots present on the dorsal surface. Eastern Pacific spec-
imens typically possess a light cream body coloration with
“a few” black pigment spots on the dorsum (MCDONALD,
1977). BROWN (1980), however, reports that British spec-
imens of 7. adspera exhibit a variable density in black
“speckling.” In several specimens collected in Marin
County, the black spots were so dense that the dorsum
appeared black. Along with these darkly pigmented in-
dividuals were collected specimens that exhibited the typ-
ical coloration pattern. The radula of a darkly pigmented
specimen agrees with the radula of 7. adspera as depicted
in BRowN (1980).
ACKNOWLEDGMENTS
I would like to thank Dr. David W. Behrens and two
anonymous reviewers for their critical review of this pa-
per.
LITERATURE CITED
BEHRENS, D. W. 1980a. Pacific coast nudibranchs. A guide to
the opisthobranchs of the northeastern Pacific. Sea Chal-
lengers, Los Osos, Calif. 112 pp.
BEHRENS, D. W. 1980b. A review of the literature on the
opisthobranch fauna of San Francisco Bay. Opisthobranch
Newsletter 12(4-12):34-37.
BeRTSCH, H. & S. JOHNSON. 1982. Three new species of dorid
nudibranchs (Gastropoda: Opisthobranchia) from the
Hawaiian Islands. Veliger 24(3):208-218.
Brown, G. H. 1980. The British species of the agdhdaczan
Paral Tergipedidae (Gastropoda: Opisthobranchia) with a
discussion of the genera. Zool. J. Linn. Soc. 69:225-255.
Cooper, J. W. 1980. The influence of predation upon Tubu-
laria crocea. In: P. Tardent & R. Tardent (eds.), Develop-
ment and cellular biology of coelenterates. Elsevier North
Holland Biomedical Press. pp. 281-286.
GODDARD, J. 1973. Opisthobranchs of San Francisco Bay.
Tabulata 6(4):8-10.
GosLINER, T. M. 1968. A new record of Corambella steinbergae
Lance, 1961. Veliger 11(2):147.
GosLINER, T. M. 1981. The South African Janolidae (Mol-
lusca: Nudibranchia) with descriptions of a new genus and
two new species. Ann. S. Afr. Mus. 86(1):1-42.
GOsLINER, T. M. 1982. The genus /anolus (Nudibranchia:
Arminacea) from the Pacific coast of North America, with
a reinstatement of Janolus fuscus O'Donoghue, 1924. Veliger
24(3):219-226.
GosLinER, T. M. & R. J. GRIFFITHS. 1981. Description and
revision of some South African aeolidacean Nudibranchia
(Mollusca, Gastropoda). Ann. S. Afr. Mus. 84(2):105-150.
GosLINER, T. M. & G. C. WILLIAMS. 1970. The opistho-
branch mollusks of Marin County, California. Veliger 13(2):
175-180.
GOSsLINER, T. M. & G. C. WILLLAMS. 1973. Additions to the
opisthobranch mollusks of Marin County, California, with
notes on their natural history. Veliger 15(4):352-354.
W. B. Jaeckle, 1983
JAECKLE, W. B. 1981. New distributional records for two Cal-
ifornia nudibranchs. Veliger 23(3):240.
Marcus, E. 1961. Opisthobranch mollusks of California. Ve-
liger 3(Suppl. 1):1-85.
Marcus, E. 1964. A new species of Polycera (Nudibranchia)
from California. Nautilus 77(4):128-131.
McDonaLbD, G. R. 1977. A review of the nudibranchs of the
California coast. Master’s Thesis, California State Univer-
sity, Hayward. 1x + 337 pp.
Page 95
STEINBERG, J. E. 1960. Rare and little known opisthobranch
mollusks from the west coast of North America. Veliger
3(2):49.
STEINBERG, J. E. 1963. Notes on the opisthobranchs of the
west coast of North America III. Further nomenclatural
changes in the order Nudibranchia. Veliger 6(2):63-67.
WILLIAMS, G. C. 1971. New record of a color variation in
Spurilla olwiae. Veliger 14(2):215-216.
The Veliger 26(2):96-100 (October 3, 1983)
THE VELIGER
© CMS, Inc., 1983
Specialized Feeding in Mitrid Gastropods:
Evidence from a ‘Temperate Species,
Mitra idae Melvill
ALLAN FUKUYAMA anpbD JAMES NYBAKKEN
Moss Landing Marine Laboratories, Moss Landing, California 95039
Abstract. The neogastropod Mitra idae Melvill is the only member of the family Mitridae on the
California coast. Although suspected of being a specialized predator, its food preferences have never
been quantified. This study documents the feeding of M. idae on sipunculans. Laboratory experiments
and gut analysis of field-collected specimens of M. idae have revealed that it is a specialized predator
preferring the sipunculan Phascolosoma agassizu Keferstein.
INTRODUCTION
MEMBERS OF THE gastropod family Mitridae are most
common in tropical waters, but some are present in tem-
perate marine waters (CERNOHORSKY, 1970; ABBOTT,
1974; McLEAN, 1978; Kay, 1979). Although PONDER
(1972) has given detailed descriptions of the digestive tract,
little is known about the diet. The few species investigated
have been shown to prey on sipunculans (KOHN, 1970,
1978; WEsT, 1979). Quantitative dietary information is
available for only two members of the family, Mitra lit-
terata Lamarck, of intertidal beaches in Hawaii, where it
specializes on the sipunculan worms, Phascolosoma spp.
and Aspidosiphon elegans Chamisso and Eyserhardt (KOHN,
1970), and Mitra flavocingulata of Easter Island, which
KOHN (1978) has reported feeding on a species of Phas-
colosoma. TAYLOR (1975) has found juveniles of Mitra
assimilis in Hawaii to feed on small mollusks under lab-
oratory conditions.
There is some uncertainty as to the number of Mitra
species occurring along the central California coast. WEST
(1979) reports two, M. idae and M. catalinae, which, he
reports, differ in radula structure and proboscis morphol-
ogy, but which are otherwise alike externally except for
size, M. catalinae being less than 30 mm in length. How-
ever, MCLEAN (1978) considers M. catalinae synonymous
with M. idae. ABBOTT (1974) questioned whether it was
a dwarf form of M. idae, and Morris et al. (1980) men-
tion only M. dae. If there are two species virtually indis-
tinguishable externally except for size as WEST (1979)
has suggested, it means that small animals (<30 mm) may
be either juvenile M. idae or M. catalinae, and would be
indistinguishable without dissection. We were not aware
of the potential presence of two species until this study
was completed and specimens had been discarded after
gut dissection; thus, we were unable to undertake radula
and proboscis dissections of small specimens to attempt to
verify WEST’s (1979) contention. Therefore, those speci-
mens that we have considered here as juvenile M. idae
(<28 mm) could be a mixture of the two species if WEST’s
(1979) contention that there are two species is substanti-
ated by other malacologists. In either case, this does not
invalidate our main argument of dietary specialization re-
gardless of size. We prefer, pending presentation of more
evidence, to follow MCLEAN (1978) and consider all Cal-
ifornia mitrids as members of one species, M. idae.
Mitra idae Melvill is restricted to kelp forests and the
low intertidal zone (MCLEAN, 1978; Morris et al., 1980).
Previous studies of this species have dealt with taxonomy
and radular arrangement (CERNOHORSKY, 1966, 1970;
Coan, 1966; CATE, 1967), functional morphology (WEST,
1979), and reproductive patterns and behavior (CATE,
1968; CHEss & ROSENTHAL, 1971; KELLOGG & LINDBERG,
1975). Although Morris e¢ al. (1980) report M. idae to
be a specialized carnivore, no documentation is provided,
nor is the prey identified. Moreover, CATE (1968) was
unsuccessful in feeding a variety of potential prey items
to M. idae in laboratory aquaria. She did not report
whether sipunculans were offered to the M. idae. WEST
(1979), however, has observed M. idae to feed upon the
sipunculan Phascolosoma agassizu and the vermetid gas-
tropod Petaloconchus montereyensis in the laboratory. His
A. Fukuyama & J. Nybakken, 1983
accounts represent the most complete descriptions of feed-
ing in the species.
The present study further quantifies the diet of free-
living Mitra idae and establishes preferences in laboratory
experiments. This information should help to establish the
role of predation by M. :dae in the kelp forest and the
more general occurrence of sipunculan feeding within the
family. Other species and genera remain to be studied to
establish a general pattern of specialized feeding on si-
punculan worms.
METHODS
The main study area was the kelp forest off Point Ca-
brillo, Pacific Grove, California (36°37'N; 121°53’W).
Additional collection of Mitra idae for gut content analyses
was done off Del Monte Beach, Pacific Grove (36°37'N;
121°53’W), and Stillwater Cove (36°33’N; 121°56’W)
(Figure 1). Descriptions of these kelp forests are given in
Lowry & PEARSE (1973) for Point Cabrillo, in BURNETT
(1972) and HOFFMAN (1981) for Del Monte Beach, and
in FOSTER (1982) for Stillwater Cove.
All sampling and collecting were done with SCUBA.
Estimates of abundance of M. idae were made at Point
Cabrillo in April and May, 1981. Water depth varied
from 5 to 10 m. Random samples were taken along 25-m
transects within a 0.25-m* quadrat. All M. idae found
within these quadrats were counted and measured. Ani-
mals used for gut-content analyses were collected haphaz-
ardly during day and night, and were boiled shortly after
collection to stop further digestion. After recording wet
weight and measuring length from the apex of the shell
to tip of siphonal canal, each shell was cracked open and
the digestive tract dissected. Prey were identified and
counted, and state of digestion noted.
Laboratory feeding experiments were conducted to doc-
ument prey preferences employing two species of sipun-
culans and other potential prey, and to observe feeding
behavior. One sipunculan species, Phascolosoma agassizu,
was collected from local rocky intertidal areas and the
holdfasts of drift kelp. The other sipunculan, 7hemuste
pyroides (Chamberlain), was collected from subtidal shale.
Prey wet weights were recorded before and after feeding
experiments. One set of experiments evaluated the pref-
erence of M. idae for the two species of sipunculans. In
each experiment, one M. idae was placed in a dish with
one P. agassizu and one T. pyroides. The experiment was
repeated 2—4 times for each M. idae used. The dishes were
covered with a fine screen to prevent escape and were held
in laboratory aquaria with running sea water. Observa-
tions continued until one of the prey was consumed or
attacked. Sipunculans of similar size were used when pos-
sible; however, individuals of 7. pyroides were generally
larger than P. agassizu.
In a second set of experiments, each species of prey was
presented separately to a specimen of M. zdae. In addition
to the two species of sipunculans, M. idae was also pre-
Page 97
121° 55'W
MONTEREY
Pt. Pinos BAY
PACIFIC
OCEAN
Pt Cabrillo
4
f Pacific. AN
MN : Grove satay
Monterey :: Bee
Pt. Cypress 36°35 N
| 2 3 oe S
KILOMETERS Stillwater
Cove
Figure 1
Location of study areas in central California.
sented with the echiuroid worm Urechis caupo Fisher and
MacGinitie, and the holothuroids Eupentacta quinquese-
mita (Selenka) and Cucumaria pseudocurata Deichmann.
Urechis caupo is a close taxonomic relative of the sipun-
culans, and the two holothuroids are similar in size and
shape to sipunculans.
RESULTS
Individuals of Mitra idae were observed subtidally on rock
walls, in crevices, in sand pockets, on old holdfasts of the
kelp Macrocystis pyrifera, under the cover of red algae
(Gigartina spp. and Rhodymenia spp.) and in tube beds of
the polychaete Dzopatra ornata Moore. Although the
abundance of M. idae was only 0.81/m? (SD = 0.54; n=
106) at Point Cabrillo, individuals were seen in aggre-
gations of up to five individuals. KOHN (1970, 1978) ob-
served 0.05-0.22 Mitra litterata/m* in Hawaii and 0.12
M. flavocingulata/m? at Easter Island.
Size-frequency plots revealed two distinct size classes at
Point Cabrillo, one near 15-20 mm and the other near
40 mm (Figure 2). CHESS & ROSENTHAL (1971) found
mean shell lengths for copulating M. idae in southern
California at 35 mm for males and 51 mm for females.
Therefore, the smaller size group (<28 mm) probably
was composed mostly of juveniles or a mixture of juveniles
and M. catalinae.
The gut contents of 41 M. :dae were examined (Table
1). Three of these individuals were collected at Stillwater
Cove, six from Del Monte Beach, and the remaining an-
Page 98
N=39
FREQUENCY
O 8 I6 24 32 40 48
LENGTH (mm)
Figure 2
Length-frequency histograms for Mitra idae collected at Point
Cabrillo. Note the separation of a large (“adult”) and small
(“juvenile”) size class.
imals from Point Cabrillo. Food was found in 22 guts
(54%). Sixteen guts contained whole sipunculans or frag-
ments. Five had unidentifiable organic matter, and one
gut had the remains of what appeared to be a nemertean
worm. The sipunculan was identified as Phascolosoma
agassizu in 13 of the 16 guts. Only five M. idae were
collected at night. These were all collected at Point Ca-
brillo. Two of these individuals had empty guts, two con-
tained fragments of P. agassizi, and one had fragments of
a nemertean. Most of the 16 juvenile M. idae had empty
guts; however, one contained part of a P. agassizi, and
The Veliger, Vol. 26, No. 2
Table 2
Choice of prey when Mitra idae was offered both sipun-
culans, Phascolosoma agassizu and Themiste pyroides. Phas-
colosoma agassizi was preferred in every experiment.
Number
of trials Prey consumed
Mitra #1 5 Phascolosoma (5) Themiste (0)
Mitra #2 6 Phascolosoma (4) Themiste (0)
Mitra #3 3 Phascolosoma (1) * Themiste (Q)
14 10 0
* Phascolosoma attacked but later released (see text).
five others contained unidentifiable organic matter. Among
the 25 adults, two contained whole specimens of P. agas-
sizit (<0.1 g), and 10 had parts of this species. The si-
punculan prey in three adult guts could not be identified
to species.
The two-choice feeding experiments indicated that Mz-
tra idae has a strong preference for one of the two sipun-
culan species. Phascolosoma agassizii was attacked in 10 of
14 trials. Themiste pyroides was not attacked (Table 2).
Feeding experiments containing one species of potential
prey showed the same pattern. Phascolosoma agassizii was
consumed in 30 of 45 trials (67%). Themuste pyroides was
not consumed in any of five exposures to M. idae (Table
3). Fewer trials were made with 7. pyroides because of
the longer duration of each experiment. In one experi-
ment, a specimen of M. dae was starved for 17 days prior
to exposure to a 7. pyroides. The T. pyroides was attacked
and held by the proboscis of M. idae for over six hours
before it was released. However, the M. idae did not con-
sume the 7. pyroides, which suffered no apparent damage
Table 1
Gut contents of Mitra idae collected at three areas in central California and in
“adult” and “juvenile” sizes from all areas.
Number of guts
examined empty
Area
Stillwater Cove 3 0
Del Monte Beach 6 1
Point Cabrillo 3B) 18
41 19
Size of Mitra idae
“Juveniles” <28 mm 16 10
“Adults” =>28 mm 25 ‘39.
41 19
* Fragment of nemertean worm.
Number
Amorphous
Number with organic
sipunculans matter Other*
0 3 0
5 0 0
1 2 i
16 5 1
1 5 0
15 0 i
16 5 1
A. Fukuyama & J. Nybakken, 1983
Page 99
Table 3
Feeding experiments offering Mitra idae either one or the
other of the sipunculans, Phascolosoma agassizu or The-
muste pyroides. Only P. agassizii was consumed.
Number Total Number Pierced Attacked,
of number — eaten and not
Prey species trials consumed whole eaten eaten
Phascolosoma 45 30 25 5 1
Themiste 5 0) 0) 0) 1
from the attack, and it remained alive in a holding tank.
Mitra idae neither attacked nor consumed the three sipun-
culan-like prey, Urechis caupo, Eupentacta quinquesemita
and Cucumaria pseudocurata, in similar feeding experi-
ments.
Laboratory feeding observations indicated two methods
of attack and consumption of the Phascolosoma agassizit.
Prey either were ingested whole or the integument was
punctured by the radula and the internal contents re-
moved through the hole, presumably by a mechanism de-
scribed by WEsT (1979). Considering all experiments,
81.5% of the P. agassizii were consumed whole (n = 40).
Prey weighing less than 0.3 g were always ingested whole,
but larger individuals (up to 0.8 g) were taken whole as
well. Only seven individuals were eaten by puncturing the
integument of the sipunculan. These prey were relatively
large compared to those eaten whole, and ranged in size
from 0.3 to 0.76 g (Figure 3). The weight loss of pierced
prey averaged 64 + 17% (n =7) and all pierced animals
died.
DISCUSSION
Mitra idae seems to be a specialized carnivore. Although
we have tested only one other sipunculan species, gut con-
tents and laboratory feeding experiments indicate that the
sipunculan Phascolosoma agassizu is the dominant or pre-
ferred prey. Phascolosoma agassizu is the most abundant
sipunculan at all three study areas on the Monterey Pen-
insula (HOFFMAN, 1981; personal observations). Despite
the presence of another sipunculan, Themiste pyroides, in
the field (HOFFMAN, 1981) and in feeding experiments,
this species was not consumed by the gastropod (Tables
2, 3). An echiuran worm and two holothurians also were
not eaten in laboratory feeding experiments. Moreover,
the guts of M. idae collected in the field did not contain
any of the abundant polychaete groups that co-occur with
M. idae (e.g., onuphids, terebellids, sabellids, syllids).
Specialized feeding on sipunculan worms was first es-
tablished by KOHN (1970, 1978) for the tropical species
Mitra litterata and M. flavocingulata. Now, evidence sug-
gests a similar situation for the temperate species M. idae.
Although three species is a small sample of the 500 or so
OD Prey consumed whole n=32
W Prey with radula hole n=7
FREQUENCY
O Ol 02 03 04 05 06 O7 08
PREY WEIGHT (g)
Figure 3
The relationship between the size of Phascolosoma agassizi and
the method of prey consumption. Smaller prey were generally
eaten whole and only larger individuals were eaten by punctur-
ing the integument of the prey and inserting the proboscis.
species from this family, the geographical separation of
M. idae from M. litterata and M. flavocingulata suggests
that a general feeding pattern concentrating on sipuncu-
lans may emerge, at least for this genus. Indeed, WEST
(1979) has determined that the epi-proboscis of M. idae
functions to locate, retrieve, and hold soft-bodied prey, in
particular, sipunculans. Perhaps sipunculan worms will
be the dominant prey for the entire family. Present know]-
edge does not allow a critical evaluation of this hypothesis,
but the distinct morphological similarities in the alimen-
tary canal among members of the family Mitridae re-
ported by PONDER (1972) would argue for this.
Laboratory feeding observations indicated two modes of
prey consumption for Mitra idae. A few sipunculans were
eaten by puncturing the integument, inserting the pro-
boscis, and removing the body contents, as WEST (1979)
has described; but most were consumed whole, especially
the smaller-sized prey. The proboscis of mitrids may be
extended the length of the shell (WILSON & GILLETT,
1972; personal observations). The ability to extend the
proboscis a long distance is of practical importance in
feeding upon prey that lodge deep in crevices, holdfasts,
or other substrata. The two modes of consuming prey also
may be of significance in that the extraction of a strongly
wedged sipunculan is not necessary. The frequency of
puncture feeding is difficult to assess in the field, as empty
guts can indicate either the absence of prey or faster diges-
tion of the internal contents of a pierced prey compared
to the outer integument of an animal consumed whole.
Gut contents and laboratory experiments suggest that
the feeding habits of Mutra idae may be more closely re-
lated to behavioral preferences and not to prey availabil-
ity. The ability to survive without food for at least 8-12
months (CATE, 1968; personal observations) supports the
Page 100
idea that prey availability may not be of critical impor-
tance. Size selective predation also may be feasible. Evi-
dence from the few whole sipunculans found in gut con-
tents of M. idae, as well as laboratory observations, seem
to support this idea. Perhaps future studies will reveal
important similarities in the foraging tactics of mitrid gas-
tropods that will allow generalizations to be made about
the family. Specialized feeding on sipunculan worms by
tropical and a temperate Mitra suggests that similar evo-
lutionary processes affected the development of these
predator-prey interactions.
ACKNOWLEDGMENTS
We thank Michael Kellogg, Valerie Hironaka, Tim
Herrlinger, John Oliver, and Mark Silberstein for re-
viewing an early draft of the paper. We thank Hopkins
Marine Station of Stanford University for use of their
facilities. Special thanks go to Lynn McMasters for draw-
ing the figures and Sheila Baldridge for her help in ob-
taining library material. Finally, the discussions with Alan
Kohn and John Oliver greatly aided in the preparation
of the paper. We also appreciate the suggestions of several
anonymous reviewers.
LITERATURE CITED
AsBBoTT, R. T. 1974. American seashells, 2nd ed. Van Nos-
trand Reinhold Co. 663 pp.
BuRNETT, N. A. 1972. The ecology of the benthic community
of bivalve molluscs in the shale at the Monterey sewer out-
fall. Master’s thesis, San Francisco State Univ. 56 pp.
CaTE, J. M. 1967. The radulae of nine species of Mitridae.
Veliger 10:192-195.
CaTE, J. M. 1968. Mating behavior in Mitra idae Melvill,
1893. Veliger 10:247-252.
CERNOHORSKY, W. O. 1966. A study of mitrid radulae and a
tentative generic arrangement of the family Mitridae (Mol-
lusca: Gastropoda). Veliger 9:101-126.
CERNOHORSKY, W. O. 1970. Systematics of the family Mitri-
dae and Volutomitridae. Bull. Auckl. Inst. Mus. 8:1-190.
The Veliger, Vol. 26, No. 2
CHEss, R. J. & R. J. ROSENTHAL. 1971. On the reproductive
biology of Mitra idae (Gastropoda: Mitridae). Veliger 14:
172-176.
Coan, E. 1966. Nomenclatural units in the gastropod family
Mitridae. Veliger 9:127-137.
FosTeR, M. 1982. The regulation of macroalgal associations
in kelp forests. In: W. Srivastava (ed.), Synthetic and deg-
radative processes in macrophytes. DeGruyter and Co., Ber-
lin. pp. 185-205.
HoFFMAN, R. G. 1981. The ecology of the benthic and endo-
lithic communities of a rocky reef in the kelp beds off Del
Monte Beach, Monterey, California. Master’s thesis, U.S.
Naval Postgraduate School. 117 pp.
Kay, E. A. 1979. Hawaiian marine shells. Reef and shore
fauna of Hawaii, Section 4. Mollusca. Bernice P. Bishop
Museum Spec. Publ. 64(4). 653 pp.
KeELLoGG, M. G. & D. R. LINDBERG. 1975. Notes on the
spawning and larval development of Mitra idae Melvill
(Gastropoda: Mitridae). Veliger 18:166-167.
Koun, A. J. 1970. Food habits of the gastropod Mitra litterata
Lamarck: relation to trophic structure of the intertidal ma-
rine bench community in Hawaii. Pac. Sci. 24(4):483-486.
Koun, A. J. 1978. Gastropods as predators and prey at Easter
Island. Pac. Sci. 32(1):35-37.
Lowry, L. W. & J.S. PEARSE. 1973. Abalones and sea urchins
in an area inhabited by sea otters. Mar. Biol. 23:213-219.
McLean, J. H. 1978. Marine shells of southern California.
Science Series 24, Nat. Hist. Mus. of L.A. County. 104 pp.
Morris, R. H., D. P. ABBoTT & E. C. HADERLIE. 1980. In-
tertidal invertebrates of California. Stanford Univ. Press,
Stanford, Calif. 690 pp.
PoNDER, W. F. 1972. The morphology of some mitriform
gastropods with special reference to their alimentary and
reproductive systems (Neogastropoda). Malacologia 11(2):
295-342.
TayLor, J. B. 1975. Planktonic prosobranch veligers of Ka-
neohe Bay. Doctoral thesis, University of Hawaii, Hono-
lulu.
West, T. L. 1979. Structure, function, and functional mor-
phology of Mitra idae Melvill 1893 and M. catalinae Dall
1920. Master’s thesis, University of the Pacific. 97 pp.
WILSON, B. R. & K. GILLETT. 1972. Australian shells. Charles
Tuttle Co. 168 pp.
The Veliger 26(2):101-105 (October 3, 1983)
THE VELIGER
© CMS, Inc., 1983
Homing in the West Indian Chiton
Acanthopleura granulata Gmelin, 1791
DAVID MOOK
Harbor Branch Foundation, Inc., R.R. 1, Box 196, Ft. Pierce, Florida 33450
Abstract. The homing behavior of the chiton Acanthopleura granulata was studied on high-,
moderate-, and low-energy rocky shores in the Bahamas. Chitons on low-energy shores tended to home
more frequently than chitons on higher-energy shores. Chitons on higher-energy shores tended to make
more frequent nighttime excursions from their home and to travel greater distances than chitons on
low-energy shores, possibly because lower food availability on higher-energy shores may force the
chitons to increase their grazing effort.
INTRODUCTION
HOMING IS A very common phenomenon in some groups
of mollusks. It has been described in several species of
gastropods (MCFARLANE, 1981; WELLS, 1980; Cook,
1979; CoLLINs, 1977; MacKay & UNDERWOOD, 1977;
and others) and chitons (GLYNN, 1970; THORNE, 1968).
Acanthopleura granulata Gmelin, 1791, a West Indian chi-
ton, is very common on the intertidal limestone shores in
the Bahamas. Individuals generally remain stationary on
their rock substratum during the daylight hours and for-
age for endolithic and surficial algal food at night (GLYNN,
1970). Unlike that of some other species of chitons, the
foraging of A. granulata does not seem to be influenced by
tidal height (NEWELL, 1979). Upon completion of its for-
aging activity, A. granulata often returns (homes) to its
original site of attachment. Because individuals do not
always come to rest exactly on their old site of attachment
and often orient themselves differently (GLYNN, 1970), the
term “homing” as used in this study is not being used in
the strictest sense (COLLINS, 1977). In this study, I de-
scribe the differences in homing behavior of individual
Acanthopleura granulata inhabiting high-, moderate-, and
low-wave energy shorelines in the Bahamas.
MATERIALS anp METHODS
In order to compare homing activity of Acanthopleura
granulata on high-, moderate-, and low-energy shorelines,
observations were made on various rocky limestone (Kar-
renfeld) (GARY et al., 1974) shorelines in the Bahama
Island chain (Figure 1). High-energy zones (Stations 1,
4, 6, 7) were on shorelines exposed to the open ocean and
were generally subjected to surf of one to several meters
in height. These shorelines were usually wetted by spray
and wave swash for a large part of the day. Moderate-
energy shorelines (Stations 5, 8) were exposed to some
waves and spray at high tides and during windy weather.
Low-energy shorelines (Stations 2, 3) were exposed to
little or no wave or spray activity and were wetted only
at flood tides when water covered the substrate.
Individual Acanthopleura granulata and their attach-
ment sites (=homes) were marked with nail polish. The
following day, the marked homes were checked to deter-
mine whether the chitons were present or absent from
where they were marked the previous day. If the chiton
was absent from the home it occupied the previous day,
the animal was located (if possible) and its new site of
attachment (home) was marked. The distance between the
original and new home was measured. If the animal could
not be located, it was counted as absent. Observations
were made from two (Indian Cay) to six (San Salvador)
consecutive days.
Because many chitons (especially in low- and moderate-
energy zones) were generally at their original home when
observed each day, observations also were made on nights
when low tides occurred to determine whether those an-
imals were foraging at night and returning to their homes
or simply were not leaving their homes at all. The dis-
tances between the foraging chitons and their homes were
measured. Personal safety considerations prevented night-
time observations on high-energy shores.
A Student’s ¢ test was used to compare distances trav-
eled between chitons (Acanthopleura granulata) in low-
energy areas and chitons in moderate-energy areas. Be-
Page 102
The Veliger, Vol. 26, No. 2
— is. 9
BLACK ROCK LN %
14
A 8 9
26°N
——4
30km
! o
js 76°W
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e,
NEW PROVIDENCE SS. ‘>
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&
‘
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Ly
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oS Guile
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ae \/6
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Figure 1
Localities where observations were made. 1: Indian Cay, near West End, Grand Bahama Island. 2, 3, 4: Black
Rock, near Moors Island, Abaco Chain. 5, 6: North Point, San Salvador Island. 7, 8: Barkers Point, San Salvador
Island.
cause an F,,,, test indicated that distance data were not
normal, all distance data were transformed using a log
transformation.
Caloric values of substrata in a moderate- (Station 8)
and low- (Station 2) energy zone were compared. Samples
of the limestone substrate were taken by scrubbing the
substrate with a wire brush and rinsing the loosened lime-
stone and its associated endolithic and surficial algae into
a jar. The samples were kept frozen until they were re-
turned to the laboratory where they were filtered, dried,
and ground into a powder. Samples were mixed with ben-
zoic acid (50% acid, 50% sample) and their caloric value
measured in a Phillipson microbomb calorimeter (PHIL-
LIPSON, 1964).
Because the topography and density of the substratum
were similar on all islands studied, caloric values are re-
ported in calories per milligram of substratum rather than
in calories per area of substratum. Irregularities in the
substratum surface made it difficult to remove limestone
evenly from a specific area. Twelve replicates were done
for each sample. A ¢ test was used to compare the caloric
value of samples taken from low- and moderate-energy
zones.
RESULTS
From a total of 162 observations, about 43% of the Acan-
thopleura granulata had moved from the point at which
they were marked the previous day. Far fewer chitons
were found at the point where they were marked in high-
energy zones (15%) than in moderate- (56%) or low- (93%)
energy zones (Figure 2). Although only a small number
of chitons observed in low-energy zones were found absent
from their home the following day, nighttime observations
showed that 59% of the marked chitons in low-energy
zones were away from their home at night. All of these
chitons had returned to their home by morning. In mod-
erate-energy zones, about 70% of the marked chitons were
observed away from their home at night, but only 56% of
these chitons had returned back to their home by morning
(Figure 3). Since nighttime observations could not be made
in high-energy zones, it is not known whether the chitons
D. Mook, 1983
Page 103
100
a5)
5
O 50
co)
ae
25
O
Low Moderate High
Energy Energy Energy
N=44 N=86 N=32
Figure 2
Percent of chitons found at marked sites one day after marking.
N = total number of animals observed.
that were present at the point of marking the following
day had homed or simply had not moved during the night.
Acanthopleura granulata in low-energy zones which were
not observed at their home the following day (only three)
were observed from 5 to 35 cm away from their home. In
moderate-energy zones, chitons which had not returned to
their home by the following day were observed 5 to 500
cm from their home (Table 1). No distance measurements
were done with high-energy-zone chitons because only a
small percentage of the marked chitons in the high-energy
zone were found the following day. The fact that marked
chitons were not found within several meters of their home
suggests that either these chitons could have traveled far-
ther from their home than moderate-energy-zone chitons
and relocated in areas that were inaccessible, or they were
removed by predators or wave action. A ¢ test detected no
significant difference between the distances of low-energy-
zone chitons and moderate-energy-zone chitons from their
home. The reason no difference was detected could be due
to the small number of individuals that did not home in
the low-energy zone; this would make a significant dif-
ference difficult to detect. At night, chitons (Acanthopleura
granulata) in moderate-energy zones ranged significantly
100
(GS)
100
pausinjar %
25
pauinjas %,
@)
Low Moderate
Energy Energy
N=13 N=23
Figure 3
Percent of chitons observed away from site of marking at night
in moderate- and low-energy zones. Solid line inside bar indi-
cates percentage of these animals which had returned to the
marked area the following morning.
farther (6-65 cm) from their home than chitons in low-
energy zones (2~30 cm; P < 0.05) (Table 1).
Caloric values of the substrate at the moderate-energy
site were significantly lower (x = 0.1767 cal/mg) than the
caloric value of the substrate at the lower energy site (x =
0.5056 cal/mg; P < 0.05).
DISCUSSION
The observations in this study suggest that Acanthopleura
granulata living in lower-energy zones may have a greater
tendency to stay attached to their home than those living
in higher-energy zones. When chitons in lower-energy
zones do leave their home to graze, they tend to travel
shorter distances and to have a greater tendency to return
to their home than do chitons in moderate- and high-
energy zones.
The reasons for development of homing in chitons are
unclear. Several explanations, such as protection from dis-
lodgment (LINDBERG & Dwyer, 1983; COLLINs, 1977),
Page 104
The Veliger, Vol. 26, No. 2
Table 1
Distance (cm) that chitons were found away from the
point of marking (home) the night and day following
marking. NS means ¢ value not significant at P = .05.
Day after Night after
marking marking
Low energy
Range (cm) 5-35 2-30
X (n) 18.3 (3) 12.00 (11)
Moderate energy
Range (cm) 5-500 6-65
X (n) 61.12 (32) 36.22 (9)
t value 1.37 (NS) DAZ
predator avoidance (WELLS, 1980), maximum utilization
of food resources (MacKay & UNDERWOOD, 1977), and
protection from desiccation (VERDERBER et al., 1983;
COLLINS, 1977; and others) have all been suggested for
other homing mollusks. It is unlikely that protection from
dislodgment is an important reason for homing in Baha-
mian Acanthopleura granulata because chitons in high-en-
ergy zones, where dislodgment is more likely due to high
wave activity, have a lesser tendency to home. Whether
homing is an important mechanism for predator avoidance
was not determined. However, little evidence of predation
and few predators (except humans at some sites) were
observed at any of the study sites, suggesting that homing
may not be important for predator avoidance in the Ba-
hamas.
It is also not clear whether Bahamian Acanthopleura
granulata home for protection against desiccation. The fact
that chitons home less in high-energy areas, which are
frequently wetted by wave action, could indicate that
homing may be an adaptation to prevent desiccation.
However, because homing may be accomplished by olfac-
tion and/or trail retracing (MCFARLANE, 1981; Cook,
1979; THORNE, 1968), the reduced homing in high-energy
areas may be caused simply by trails and olfactory stimuli
being washed away by wave action. If homing is impor-
tant for the prevention of desiccation, the loss of a trail to
home could be of little consequence for chitons in high-
wave-energy areas where desiccation is not a major prob-
lem.
The lower caloric food value of the moderate-energy
substrate zones may explain the more frequent and more
distant nighttime excursions of chitons (Acanthopleura
granulata) in moderate- (and possibly high-) energy zones.
Studies with filter-feeding bivalves (WINTER, 1978) and
grazing winkles (Littorina littorea Linné, 1758) (NEWELL
et al., 1971) have shown that feeding effort (filtration rates
or radular movement) tended to decrease as food became
more available. For example, winkles tended to have higher
radula movement rates when their food supply was lim-
ited on a temporal basis (NEWELL et al., 1971). NEWELL
(1979) suggested that when food availability was lower,
feeding effort may have had to increase in order for the
organism to continue to get enough food to sustain itself.
In the case of the chitons examined in this study, the lower
caloric value of the moderate-wave (and possibly high-)
energy substrata may force animals in these zones to for-
age at more frequent intervals and to travel longer dis-
tances (increase grazing effort) in order to obtain the nec-
essary calories to sustain themselves.
Other factors in addition to wave exposure or food
availability may affect homing behavior in chitons. Ele-
ments such as inter-island variability, differences in sub-
strate morphology, and differences in substrate productiv-
ity have not been addressed in this study and would be
interesting subjects for future studies with Acanthopleura
granulata.
ACKNOWLEDGMENTS
I wish to thank Richard Houbrick, Paul Mikkelsen, and
Robert Virnstein for their helpful comments on the manu-
script. I am grateful to Pat Linley for proofreading the
manuscript, and I am indebted to Charles Hoskin for his
support during this study. I would like to thank Donald
and Kathy Gerace of the College Center of the Finger
Lakes field station on San Salvador for their hospitality
and help. This is Harbor Branch Foundation Contribu-
tion No. 339 and CCSL Contribution No. 64-B.
LITERATURE CITED
Co.uins, L. S. 1977. Substrate angle, movement and orien-
tation of two sympatric species of limpets, Collisella digitalis
and Collisella scabra. Veliger 20:43-48.
Cook, A. 1979. Homing in the Gastropoda. Malacologia 18:
315-318.
Gary, M., R. MCAFEE, JR. & C. Wor. 1974. Glossary of
geology. American Geological Institute. Washington, D.C.
xiv + 805 pp. + 52 pp.
GLynn, P. W. 1970. On the ecology of the Caribbean chitons
Acanthopleura granulata Gmelin and Chiton tuberculatus
Linné: density, mortality, feeding, reproduction, and growth.
Smithsonian Institution Press No. 60: 21 pp.
LINDBERG, D & K. Dwyer. 1983. The topography, formation
and role of the home depression of Collisella scabra (Gould)
(Gastropoda: Acmaeidae). Veliger 25:229-234.
MacKay, D. A. & A. J. UNDERWOOD. 1977. Experimental
studies in the intertidal patellid limpet Cellana tramoserica
(Sowerby). Oecologia 30:215-237.
McFar ane, I. D. 1981. In the intertidal homing gastropod
Onchidium verruculatum (Cuv.) the outward and homeward
trails have a different information content. J. Exp. Mar.
Biol. Ecol. 51:207-218.
NEWELL, R. C. 1979. Biology of intertidal animals. Marine
Ecological Surveys L & D, Faversham. ix + 781 pp.
NEWELL, R. C., V. I. PYE & M. AHSUNULLAH. 1971. Factors
affecting the feeding rate of the winkle Littorina littorea.
Mar. Biol. 9:138-144.
PHILLIPSON, J. 1964. A miniature bomb calorimeter for small
biological samples. Oikos 15:130-139.
THORNE, M. J. 1968. Studies on homing in the chiton Acan-
D. Mook, 1983
thozostera gemmata. Aust. J. Mar. Freshwater Res. 19:151-
160.
VERDERBER, G. W., S. B. Cook & C. B. Cook. 1983. The
role of the home scar in reducing water loss during aerial
exposure of the pulmonate limpet Siphonaria alternata (Say).
Veliger 25:235-243.
Page 105
WELLS, R. A. 1980. Activity pattern as a mechanism of pred-
ator avoidance in two species of acmaeid limpet. J. Exp.
Mar. Biol. Ecol. 48:151-168.
WINTER, J. 1978. A review of the knowledge of suspension
feeding in lamellibranchiate bivalves, with special reference
to artificial aquaculture systems. Aquaculture 13:1-33.
The Veliger 26(2):106-112 (October 3, 1983)
THE VELIGER
© CMS, Inc., 1983
Aspects of Reproduction in Some Enoploteuthid
Squids from Hawaiian Waters!
by
LISA M. BOUCHER
Mid-Pacific Research Laboratory, Enewetak, Marshall Islands,
P.O. Box 1768, APO San Francisco 96555
Abstract.
This study investigates aspects of reproduction of three enoploteuthid squid species, Pteryg-
oteuthis microlampas Berry, Pyroteuthis addolux Young, and Abraliopsis sp., captured in Hawaiian
waters during a 17-month, midwater-trawl sampling program. Pterygioteuthis microlampas differed from
the other species in having smaller ova and higher relative fecundity. Juveniles of P. microlampas were
most often caught in spring months, indicating a seasonal spawning tendency in this species. Seasonality
of spawning in one or more species also was indicated by fall and winter peaks in enoploteuthid larval
abundance. Although the majority of females in the larger size classes had mated prior to capture, only
a minority of ova in any specimen were mature and the ratios of female gonad dry weight to total body
dry weight were generally low, suggesting that full reproductive maturity was not observed in these
specimens. In light of these results, net avoidance is considered, as is the possibility that partially spent
females were captured. Also raised is the question of whether these species are able to spawn in more
than one spawning season.
INTRODUCTION
APPROXIMATELY 50 species of pelagic squid are known to
occur in Hawaiian waters (YOUNG, 1978). Most of these
are small in size and low in abundance. Those most com-
monly captured in mesopelagic trawl samples are of the
family Enoploteuthidae. Previous studies of enoploteuthid
species in Hawaii have primarily involved their system-
atics (BERRY, 1914), vertical distribution (YOUNG et al.,
1980; YOUNG, 1978; ROPER & YOUNG, 1975), photobiol-
ogy (YOUNG et al., 1980; YOUNG, 1972, 1973), and occur-
rence in the diet of larger carnivores (KING & IKEHARA,
1956; CLARKE, 1971). A few papers have treated aspects
of reproduction of enoploteuthids occurring in temperate
waters (e.g., SASAKI, 1914; OKUTANI & McGowan, 1969;
PeEaARCY, 1965). However, the life histories and reproduc-
tive biology of the Enoploteuthidae remain largely un-
studied.
The following study was undertaken to investigate fe-
cundity, size at maturity, larval abundance, seasonality,
and other aspects of reproduction of the three most com-
monly sampled enoploteuthid squid species in Hawaiian
waters. Many of the results must be considered prelimi-
' Hawaii Institute of Marine Biology Contribution No. 666.
nary due to the sampling difficulties inherent in studies of
this kind. Nevertheless, this study contributes original data
that provide new insights into the life histories of these
little-known squid species.
MATERIALS anpD METHODS
This study is based primarily on specimens collected at
approximately monthly intervals 20 km west of Oahu,
Hawaii, between August, 1977, and October, 1978. Ju-
venile and adult enoploteuthids were collected in night-
time oblique samples with a 3-m Isaccs-Kidd midwater
trawl (IKMT) and a 1.25-m diameter bongo net (BB).
Larvae (<5 mm dorsal mantle length) were taken pri-
marily in standard bongo nets (SB) of 70-cm diameter.
Each net was equipped with a flow meter and a time-
depth recorder. The IKMT had a mouth area of 7.7 m?
and a mesh of about 6 mm, except for a 1-m cod end of
333 um. The IKMT was towed at 2 m/s and was re-
trieved at 40-50 m/min. The average maximum depth
reached was 325 m (+30 m), and the average volume
filtered per tow was 101 X 10? m®. The BB mesh was 2.5
mm. It was towed at about 1.75 m/s and retrieved at 40-
50 m/min. The average maximum depth was 304 m (+6
m), and average volume filtered per net was 9434 m?*. The
standard bongo was towed at 1 m/s and retrieved at a
Ee M> Boucher, 1983
a
5000
Enoploteuthid Larval
©)
X 11000 m2 Sea Surface
pe) W SS
(e) (eo) (eo)
fe) oO oO
[e) (eo) ©)
=|
eee ee eae
POs
S
1000 it
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9
a
bod
ele te L
Page 107
Abundance
28)
ot
ee ea
ae
p= 816
[es
17
ute
@
ZB
77-8 77-9 77-10 77-ll 77-l2 78-2 78-3 78-4 78-5 78-6 78-7 78-8 78-9 78-I0 78-II
Year — Month
Figure 1
Monthly abundance estimates of enoploteuthid squid larvae (x/1000 m? of sea surface area) as determined by
nighttime standard bongo tows. Mean values and ranges are indicated; n = number of larvae (<5 mm DML)
captured.
rate of 60 m/min. The average maximum depth attained
was 224 m (+33 m) and average volume filtered was 790
m? per net. For each tow, it was assumed that the entire
sampled population occurred above the maximum depth
attained by these nets. This assumption is supported by
the vertical distribution study of YOUNG (1978). For each
month, except January, 1978, when no samples were col-
lected, 3-4 replicate IKMT tows, 2-4 standard bongo
tows, and 2 large bongo tows were taken.
All samples were preserved in 10% formalin. Squid
larvae from standard bongo tows were identified to family.
For each SB tow, the number of enoploteuthid squid lar-
vae per 1000 m? of sea surface area was estimated (after
MAyYNarD et al., 1975) by multiplying the number of lar-
vae captured by 1000 X (maximum net depth/volume fil-
tered).
Adult and juvenile enoploteuthids from BB and IKMT
tows were identified to species, sexed, and dorsal mantle
length (DML) measured. Specimens from IKMT catches
were pooled by quarter to consider seasonal trends in size
composition. K-S tests (SIEGEL, 1956) were used to esti-
mate the significance of differences observed in the size
frequency curves of Pterygiotheuthis microlampas Berry,
1913, sampled in four seasons.
Ovaries were examined and extracted from adult and
juvenile (=9 mm DML) specimens of Pterygioteuthis mi-
crolampas, Pyroteuthis addolux Young, 1972, and Abraliop-
sis sp. B (nomenclatural usage follows YOUNG, 1978). Go-
nad dry weight/total body dry weight ratios (G/S) were
determined for all dissected specimens after drying for 24
h at 60°C.
Fecundity estimates were made for 10 or more of the
largest specimens of each of the three species on the as-
sumption that the larger specimens would contain the
greatest numbers of mature ova. Individual fecundity was
determined by direct count of all yolked odcytes. Odcytes
were considered to be yolked if their nuclei were not dis-
cernible at 10 magnification. Relative fecundity, ex-
pressed as ova/g total dry weight, was used for interspe-
cific comparisons. Mann-Whitney tests (ZAR, 1974) were
used to estimate the significance of differences in relative
fecundity.
Ova size-distribution frequencies were determined by
manual dissection of the ovaries and examination of sam-
ples with a microscope. Several methods were used to
sample the ovary in an effort to develop a reliable and
accurate technique. In a total of nine specimens repre-
senting all three species, sections were examined from the
most posterior and anterior ends of the ovary, and from
the midsection. For most other specimens, only the pos-
terior terminus of the ovary was examined. The entire
ovary was examined in one specimen each of Abraliopsis
sp. B and Pterygioteuthis microlampas. In three Pyroteuthis
addolux, the entire ovary was gently teased apart and
mixed, and several samples were examined.
RESULTS
The most commonly collected squid in 57 IKMT and 28
BB tows were the enoploteuthid species Pterygioteuthis
microlampas, Pyroteuthis addolux, and Abraliopsis sp. B.
One hundred and sixteen adult and juvenile (£9 mm
Page 108
The Veliger, Vol. 26, No. 2
Prerygioteuthis microlampas
100
Cumulative Percentage
10 I 12 13 14 15
ISIE YS 2 N=
O Fall 43
O) Winter 5)
@ Spring 24
A Summer
16 17 18 19 20 2
Size Class (mm Mantle Length)
Figure 2
Cumulative size class percentages of Pterygioteuthis microlampas sampled by IKMT in four seasons. The spring
size-class distribution differs significantly from each of the others (P < .01, K-S test); n = number of specimens
captured.
DML) P. microlampas, 88 P. addolux, 51 Abralopsis sp.
B, 48 Pterygioteuthis giard: Fischer, 1895, 26 Abraliopsis
sp. A (after YOUNG, 1978), and 13 Abralia trigonura Ber-
ry, 1913, were collected.
Enoploteuthid larvae were present all year (Figure 1).
The greatest abundances of larvae occurred during. the
months of October and December, 1977, and October and
November, 1978, indicating the possibility of a seasonal
spawning trend in one or more species. The large ranges
observed in larval abundance estimates by the individual
tows are probably due to the low average number of larvae
captured per tow, but may also indicate patchiness of dis-
tribution.
The data for Pterygioteuthis microlampas (Figure 2) in-
dicate that 90% were <14 mm in spring, that all sizes
were more nearly equally represented in summer and fall,
and that only animals =15 mm were found in winter.
The size-frequency curve for spring differed significantly
(P < .01, K-S test) from that of each of the other seasons,
but no significant differences (P > .05) were found among
the other seasonal pairs. The absence of a significant dif-
ference between winter and spring or fall may have been
the result of the smaller number (n= 5) of specimens
collected in winter. Pyroteuthis addolux and Abraliopsis sp.
B showed no coherent seasonal changes in size distribu-
tion.
The ratios of female gonad dry weight to total dry weight
(G/S) were plotted against mantle length for the three
species to estimate length at onset of reproductive maturity
(Figures 3a, b, c). Increasing G/S ratios were not strictly
correlated with increasing mantle length in any species,
indicating that the onset of sexual maturity is not strictly
size dependent, or that partially spent or spawning fe-
males may have been captured. The maximum G/S ratios
for each species were found, not in the largest specimens,
but in an 18-mm (DML) Pterygioteuthis microlampas, a
40-mm Pyroteuthis addolux, and a 26-mm Abraliopsis sp.
B. The data for P. microlampas were the most scattered,
L. M. Boucher, 1983
20 A. Prerygioteuthis micro/ampas
% Gonad Dry Weight
Total Dry Weight
lO if 12 ls 18 16 Ir 16 19 20
Mantle Length (mm)
B. Pyroteuthis addo/ux
“%. Gonad Dry Weight
Total Dry Weight
% Gonad Dry Weight
Total Dry Weight
10 12 14 16 18 20 22 24 26 28
Mantle Length (mm)
Figures 3a, b, c
Percent female gonad dry weight/total body dry weight plotted
against dorsal mantle length for the three species studied.
perhaps due to a proportionally greater hydration error
in the gonad weights of the small specimens during dry
weighing.
The presence of spermatophores in the sperm recepta-
cles of females of the larger size classes revealed that most
had mated prior to capture. In Pterygioteuthis microlam-
Page 109
pas, spermatophores were usually found in females 215
mm DML. Spermatophores were usually found in female
Pyroteuthis addolux and Abraliopsis sp. B 235 and 20 mm
DML respectively; however, an occasional specimen of P.
addolux as small as 14 mm DML, an Abraliopsis sp. B of
11 mm DML, also were found bearing spermatophores.
Fecundity, ovum sizes, and G/S ratio data from the
largest individuals captured are summarized in Table 1.
Pterygioteuthis microlampas differed from the other species
in its reproductive pattern of high relative fecundity and
smaller ova. The number of yolked ova per gram dry body
weight in P. microlampas was approximately 2.9X that of
P. addolux, and 2.8X that of Abraliopsis sp. B. Both dif-
ferences were statistically significant (P < .05, Mann-
Whitney test). The largest ova of P. microlampas mea-
sured 60% of the maximum ovum diameter of the other
species.
Ova size-frequency data (Figure 4) were similar for the
three species regardless of the method used. Typically, the
percentage of yolked ova (=300 um) found in the larger
size classes increased with increasing G/S ratios. How-
ever, only a minority of ova fell within the largest size
classes (>700 um), even in individuals with the highest
G/S ratios. Ova 700 um or larger did not exceed 25% of
the total number of yolked ova in any specimen. Non-
yolked odcytes (<300 wm) accounted for an average of
63% (range 44-80%, n=10) of all odcytes present.
Therefore, only a very small percentage of the total num-
ber of odcytes present had developed into mature ova in
any of the specimens examined.
The sex ratios for adult Pterygioteuthis microlampas,
Pyroteuthis addolux, Pterygioteuthis giardi, and Abraliopsis
spp. A and B did not differ significantly from 1:1 (99%
confidence limits from TATE & CLELLAND, 1957). In the
rarely captured Abralia trigonura, 10 of 13 specimens were
females.
DISCUSSION
Although most of the adult female enoploteuthids exam-
ined in the present study had mated prior to capture, the
generally low G/S ratios and scarcity of larger ova raise
the question of whether full reproductive maturity was
observed. Mating prior to full ova maturation has been
reported for other squid species including Loligo opales-
cens Berry, 1911 (FIELDs, 1965) and Todarodes pacificus
Steenstrup, 1880 (SOEDA, 1956 fide FIELDS, 1965, as Om-
mastrephes sloant Berry, 1912), and may also occur in
Hawaiian enoploteuthids. According to FIELDs (1965),
transfer of spermatophores in L. opalescens can occur “soon
after the first few ova mature while the bulk of the gonad
products are still unripe.”
Despite the intensive sampling effort undertaken dur-
ing the present study, the ripest females may have avoided
capture. The problem of net avoidance by squid has been
discussed by many authors (e.g., HARDY, 1965; PEARCY,
1965; ROPER & YOUNG, 1975). Also, ROPER (1977) has
Page 110
30
25
% of Total Number of Ova = 300 xm
300 400 500 600 700
The Veliger, Vol. 26, No. 2
NEY 3
o—o Abra/siops’s sp. B
G/S=14.6 (3 sections)
e—e “/ferygioteuthis microlampas
G/S =10.3 (Entire ovary)
A-—-A Pyroteuthis addolux
G/S =13.6 (Random sample)
1000 =1100
1200
800 900
Ovum Diameter ( um)
Figure 4
Typical ova size-frequency data for the three species studied. Distribution of ova expressed as the percentage of
each size class relative to all ova =300 wm. n=1 specimen for each curve. Species, % gonad dry weight/total
body dry weight (G/S), and sampling method are indicated for each curve.
demonstrated that cephalopod capture rates and catch
compositions vary with different types of midwater trawls.
Unfortunately, the bias of the present samples cannot be
specified because there is no unbiased method with which
to compare them. It is noteworthy that the extent of net
avoidance by enoploteuthids seems to be less than that of
other, more powerful species. In the present study, al-
though the ommastrephid Symplectoteuthis oualaniensis
(Lesson, 1830) was frequently observed in the study area,
neither juveniles nor adults of this fast swimming species
were captured by trawl. In contrast, adult enoploteuthids
were captured occasionally even in the SB plankton tows.
Spawning specimens also may have avoided capture by
migrating into deeper waters or shallow coastal waters to
spawn. Shoreward spawning migrations are known in
other squid species, including the enoploteuthid Watasenia
Table 1
Fecundity, ovum sizes and gonad dry weight/total dry weight ratios of three enoploteuthid species. (Data from largest
individuals captured)
Individual fecundity
(No. yolked ova)
Species n x + SE
Pterygioteuthis microlampas 11 259 + 45.5
Pyroteuthis addolux 10 1259 + 205.5
Abraliopsis sp. B 10 476 + 39.8
Relative fecundity
No. yolked ova Largest ovum Gonad dry weight
Gram dry body weight diameter Total dry weight
x+ SE pm x + SE
4641 + 712.5 900 0.096 + 0.010
1609 + 168.5 1300 0.108 + 0.014
1675 + 149.5 1300 0.141 + 0.013
L. M. Boucher, 1983
scintillans Berry (SASAKI, 1914). Alternatively, if these
species mature rapidly and complete spawning in a short
period relative to their life span, or form spawning ag-
gregations, the chances of sampling them at this stage
would be quite small.
Female Loligo opalescens can lose more than 50% of
their dry body weight at spawning, approximately 40%
being weight lost by the reproductive system (FIELDS,
1965). In a mature Octopus maya (Voss and Solis, 1966),
34% of the dry body weight was attributable to dry egg
matter (VAN HEUKELEM, 1976). In this study, the highest
G/S ratio was observed in a specimen of Abraliopsis sp.
B. Only 21% of the dry body weight was attributable to
dry ovary weight. The average G/S ratios recorded (Ta-
ble 1) were much lower. The low G/S ratios could indi-
cate that partially spent or spawning females were cap-
tured. However, in other species for which information is
available, large numbers of non-yolked odcytes are not
usually present in the ovaries of spawning individuals.
SASAKI (1914) noted that most of the ova of spawning
Watasenia scintillans were “mature” and that a compar-
atively small number of immature ova were imbedded in
the ovarian tissue; unfortunately, his criteria of egg ma-
turity were not specified. KNIPE & BEEMAN (1978) found
that the ovaries of spawning L. opalescens differed cyto-
logically from immature ovaries in lacking pre-odcytes,
which were defined as odgonia smaller than approxi-
mately 59 um. In the present study, non-yolked odcytes
predominated, a large proportion of which were compa-
rable in size to the pre-odcytes of KNIPE & BEEMAN (1978).
If the most mature specimens were not avoiding cap-
ture, the low G/S ratios and ova size distributions could
suggest that these species have the potential to spawn re-
peatedly. In most species of cephalopods, death follows
mating and spawning (ARNOLD & WILLIAMS-ARNOLD,
1977). In the enoploteuthids studied, the non-yolked 06-
cytes may represent potential modes of ova for future
spawning. Further studies are clearly required before con-
clusions may be drawn concerning the reproductive habits
of these species.
Young Pterygioteuthis microlampas were most often cap-
tured during spring months, indicating a seasonal spawn-
ing tendency in this species. Seasonal spawning in one or
more species also is suggested by the peaks observed in
enoploteuthid larval abundance during fall and early win-
ter months. If the 10-12 mm juveniles of P. microlampas
which dominate the spring catch were spawned in the fall,
a growth rate of 1.8-2.0 mm/month can be conjectured
for juveniles of this species. Seasonal spawning also has
been reported in other enoploteuthid species. Watasenia
scintillans spawns in Toyama Bay, Japan in late spring
and early summer (SASAKI, 1914). In a study of pelagic
cephalopods from Oregon, seasonal spawning in a species
of Abraliopsis was suggested by the predominance of small
individuals in summer trawl samples (PEARCY, 1965).
The higher fecundity of Pterygioteuthis microlampas rel-
ative to other Hawaiian enoploteuthid species may be re-
Page 111
lated to its seasonal spawning tendency. The production
of greater numbers of offspring could function to offset
the risk of high mortality should spawning coincide with
conditions not favorable to larval survival.
ACKNOWLEDGMENTS
I am most grateful to Thomas A. Clarke for editorial
comments and guidance in all aspects of this study. I also
thank S. R. Haley, M. G. Hadfield, S. Johnson, and R.
E. Young for contributing their thoughts and suggestions.
All samples were collected through the research program
of T. A. Clarke. This study was supported by National
Science Foundation grant #OCE 77-09202 AO1, and used
the facilities of the Hawaii Institute of Geophysics and
the Hawaii Institute of Marine Biology.
LITERATURE CITED
ARNOLD, J. M. & L. D. WILLIAMS-ARNOLD. 1977. Cepha-
lopoda: Decapoda. Jn: A. C. Giese & J. S. Pearse (eds.),
Reproduction of marine invertebrates, Vol. 4, Molluscs:
gastropods and cephalopods. Academic Press, New York.
pp. 243-290.
Berry, S.S. 1914. The Cephalopoda of the Hawaiian Islands.
Bull. U.S. Bur. Fish. 32:255-362.
CxiarkE, T. A. 1971. The ecology of the scalloped hammer-
head shark, Sphyrna lewini in Hawaii. Pac. Sci. 25(2):330-
348.
FieLps, W. G. 1965. The structure, development, food rela-
tions, reproduction and life history of the squid Loligo opa-
lescens Berry. Calif. Dep. Fish Game Fish, Bull. 131(1):1-
108.
Harpy, A. H. 1965. The open sea. Part I: The world of
plankton. Riverside Press, Cambridge, England. v—xv + 322
PP.
KING, J. E. & I. I. IkKEHARA. 1956. Comparative study of the
food of bigeye and yellowfin tuna in the central Pacific. Fish.
Bull. U.S. Fish Wildl. Serv. 57:61-68.
Knipe, J. H. & R. D. BEEMAN. 1978. Histological observa-
tions on odgenesis in Loligo opalescens. In: C. W. Recksiek
& H.W. Frey (eds.), Biological, oceanographic, and acous-
tic aspects of the market squid, Loligo opalescens Berry. Cal-
if. Dep. Fish Game Fish, Bull. 169:23-33.
MaynarbD, S. D., F. V. Riccs & J. F. WALTERS. 1975. Me-
sopelagic micronekton in Hawaiian waters: faunal compo-
sition, standing stock, and diel vertical migration. Fish. Bull.,
U.S. 73:726-736.
OxkuTanl, T. & J. A. McGowan. 1969. Systematics, distri-
bution, and abundance of the epiplanktonic squid (Cepha-
lopoda, Decapoda) larvae of the California Current, April
1954—March 1957. Bull. Scripps Inst. Oceanog. 14:1-90.
Pearcy, W. G. 1965. Species composition and distribution of
pelagic cephalopods from the Pacific Ocean off Oregon. Pac.
Sci. 19(2):261-266.
Roper, C. F. E. 1977. Comparative captures of pelagic ceph-
alopods by midwater trawls. Symp. Zool. Soc. Lond. 38:61-
87.
Roper, C. F.E. & R. E. YOUNG. 1975. Vertical distribution
of pelagic cephalopods. Smithsonian Contr. Zool. 209:1-51.
Sasaki, M. 1914. Observations on Hotaru-ika, Watasenia scin-
tillans. J. Coll. Agricul. Tohaku Imperial Univ. Sapporo
6(4):75-105.
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SIEGEL, S. 1956. Nonparametric statistics for the behavioral
sciences. McGraw-Hill, New York. vii-xvii + 312 pp.
SoEDA, J. 1956. Studies on the ecology and the breeding habits
of the squid, Ommastrephes sloani pacificus (Steenstrup) in
the coastal waters of Japan. Japan Sci. Papers Hokkaido
Fish. Sci. Inst. 14:1-24.
Tate, M. W. & R. C. CLELLAND. 1957. Nonparametric and
short cut statistics. Interstate Printers and Publishers, Inc.,
Danville, Illinois.
VAN HEUKELEM, W. F. 1976. Growth, bioenergetics, and life
span of Octopus cyanea and Octopus maya. Doctoral thesis,
University of Hawaii. 224 pp.
YounG, R. E. 1972. Function of extra-ocular photoreceptors
in bathypelagic cephalopods. Deep-Sea Res. 19:651-660.
YouNG, R. E. 1973. Information feedback from photophores
and ventral countershading in mid-water squid. Pac. Sci.
27:400-404.
YOUNG, R. E. 1978. Vertical distribution and photosensitive
vesicles of pelagic cephalopods from Hawaiian waters. Fish.
Bull., U.S. 76(3):585-615.
YOUNG, R. E., E. M. Kampa, S. D. MAYNARD, F. M. MENCHER
& C. F. E. Roper. 1980. Counterillumination and the
upper depth limits of midwater animals. Deep-Sea Res. 27:
671-691.
ZAR, J. H. 1974. Biostatistical analysis. Prentice-Hall, Inc.,
New Jersey. v—xiv + 620 pp.
The Veliger 26(2):113-115 (October 3, 1983)
THE VELIGER
© CMS, Inc., 1983
Shell Repair Frequencies of ‘Two Intertidal
Gastropods from Northern California:
Microhabitat Differences
by
JONATHAN B. GELLER
Bodega Marine Laboratory, Box 247, Bodega Bay, California 94923
Abstract.
Tegula funebralis (A. Adams, 1854) and Nucella emarginata (Deshayes, 1839) from distinct
microhabitats (surge channels, tidepool, and mussel bed) at Bodega Bay, California, were examined,
and shell repairs enumerated. Frequencies of repair in samples of 7egula from each microhabitat were
significantly different from each other. All samples of Nucella differed from each other except those
from Surge Channel 2 and the mussel bed site. The significance of these results for interspecific
comparisons of shell-repair frequencies is discussed.
INTRODUCTION
THE FREQUENCY OF shell repair in populations of inter-
tidal gastropods has been used recently as an indicator of
intensity of selection for antipredator traits (VERMEIJ,
1978, 1981, 1982a). Briefly, repairs are records of sub-
lethal attacks by predators (or other shell-breaking agents),
and snails that survive such attacks will contribute more
progeny to subsequent generations than those which suc-
cumb (VERMEIJ, 1982b). Hence, where shell-repair fre-
quencies are high, it is inferred that selection for antipred-
ator traits is high. Shell breakage from agents other than
predation should, by the same reasoning, select for some
of the same shell characters. However, many morpholog-
ical features are identified as defense primarily against
predation, and scars left by predators are often distin-
guishable from other markings (VERMEIJ, 1978). Analysis
of shell repair in various gastropods (VERMEIJ, 1978) and,
in more detail, of terebrid snails (VERMEIJ et al., 1980)
reveal that repair frequencies are highest at low latitudes
and, between oceans, in the Indo-West Pacific. These
findings support other evidence that predation is a greater
hazard to snails in the tropics than to those of temperate
shores (VERMEIJ, 1978; ZIPSER & VERMEIJ, 1978;
BERTNESS ef al., 1981; MENGE & LUBCHENCO, 1981).
There are, however, possible problems with the use of
shell-repair frequencies as an indicator of predation in-
tensity, including small sample sizes, frequent reliance on
museum collections, and microhabitat-related intraspecific
variation in repair frequency. The purpose of this note is
to present data on intraspecific variation in shell-repair
frequency.
MATERIALS anp METHODS
Tegula funebralis (A. Adams, 1854) and Nucella emargina-
ta (Deshayes, 1839) were collected in the intertidal zone
adjacent to the Bodega Marine Laboratory (BML) near
Bodega Bay on the northern California coast. The inter-
tidal zone at BML consists of highly jointed granitic
benches. Live snails were collected at four distinct micro-
habitats. Specimens of 7egula were collected at two surge
channels and in a bed of the mussel Mytilus californianus
Conrad, 1837. Specimens of Nucella were collected at the
two surge channels, in the mussel bed, and also on a
vertical rock surface near a mid-intertidal tidepool. Each
snail was examined with a low-power binocular dissecting
microscope. Shell repairs were identified as jagged relief
on the surface of the body whorl. The extreme unevenness
of scars distinguish them from growth lines, which may
be prominent on these shells. Further, many scars are of
a characteristic shape produced by the peeling action of
the crabs (see VERMEIJ, 1978). Where ambiguity existed
as to the origin of a marking, that shell was scored as not-
scarred. Voucher specimens from each sample were re-
tained.
RESULTS
Frequencies of shell repairs for Tegula were dramatically
higher in the samples from the surge channels than in the
Page 114
Table 1
Percentages of Tegula and Nucella shells with shell re-
pairs, with sample size in parentheses. Code for micro-
habitats: surge channel 1 = SC1, surge channel 2 = SC2,
mussel bed = MB, tidepool = TP.
Scl SCc2 MB TP
Tegula 49.6 (250) 28.5 (200) 3.8 (177) —
Nucella 19.6 (234) 10.0 (200) 9.3 (236) 5.5 (200)
samples from the mussel bed: 123 of 250 and 57 of 200
shells from the surge channels had scars compared to 7 of
177 from the mussel bed (Table 1). Chi-square analysis
shows that each sample differs significantly from the other
two (Table 2). For Nucella, like Tegula, the samples from
the surge channels had the highest repair frequencies, with
the mussel-bed and tidepool samples next in descending
order. However, only Surge Channel 1 was significantly
different than the others (Table 2).
Interspecific comparison shows that Jegula is signifi-
cantly more scarred in the surge channel microhabitats,
whereas Nucella is more scarred in the mussel bed (Table
2)
DISCUSSION
These results show shell-repair frequencies can vary be-
tween microhabitats. To interpret interspecific differences
in shell-repair frequencies meaningfully, a range of mi-
crohabitats should be sampled. For example, a possible
misinterpretation based on mussel-bed samples would be
that Nucella is more scarred than Tegula; whereas data
pooled from several microhabitats show that Tegula is
significantly more scarred (x? = 79.2, P < 0.001). Hence,
discussion of the significance of differences in shell-repair
frequencies should treat Jegula as the more scarred species.
Although this study is not intended as a test of hypotheses
of gastropod shell evolution, it is clear from the arguments
outlined in the Introduction that one would expect selec-
tion for antipredatory traits to be higher for Tegula. How-
ever, Tegula, a typical trochid, possess few structural fea-
tures identifiable as antipredatory. In contrast, Nucella
has a narrow aperture and a short spire, both identified
as defensive (VERMEIJ, 1978). This apparent discrepancy
may be a result of an invalid comparison of phylogenet-
ically distant species; morphological constraints and po-
tential evolutionary responses may not be similar for both
species.
At present I can only speculate on the source of varia-
tion in scar frequency reported here. The surge channel
microhabitats might be more accessible to mobile preda-
tors (e.g., crabs and fishes) compared to mussel beds due
The Veliger, Vol. 26, No. 2
Table 2
Chi-square test with continuity correction of differences
in shell-repair frequencies between each sample. Code for
microhabitats as in Table 1, except prefaced by T (=Teg-
ula) or N (=Nucella). All values are significant at P <
0.05 except where marked ns (P > 0.05).
TSC1 TSC2 TMB NSC1NSC2 NMB NTP
TSC1 — 19.7 103.3 46.2 78.3 91.8 100.8
TSC2 — — 40.3 4.2 20.8 25.6 35.9
TMB — — —= WY 47 4.1 0.3 ns
NSC1 = — — — 7.1 9.3 Wea
NSC2 — — — — — 0.006 ns 2.2 ns
NMBO p= => 72 Se 1.74 ns
to unbroken connection with lower-intertidal and subtidal
levels, and perhaps due to its horizontal aspect facilitating
predator movement. For example, while diving in other
nearby surge channels, I have observed the large rock crab
Cancer antennarius Stimpson, 1856, to be abundant. Sim-
ilar densities are expected in the surge channels reported
on here. Further, wave action may at times be intense,
resulting in nonpredator-induced shell breakage. Lower
frequencies of shell repair in the mussel bed for Tegula
and tidepool for Nucella may be due to refuge from pred-
ators and wave shock afforded by these microhabitats. The
reversed trend of shell breakage frequency in the mussel
bed remains an interesting problem. Probable duropha-
gous predators in the mussel bed are the black oystercatch-
er, Haematopus bachmani Audubon, and the lined shore
crab, Pachygrapsus crassipes Randall, 1839; however, no
data are available on preferences of these predators for
Tegula or Nucella.
Finally, some repair frequencies reported here are high
compared with those reported for temperate and even some
tropical snails. For instance, VERMEIJ et al. (1980) report
average frequencies of 0.25-0.96 (where multiple scars on
a shell are counted) for tropical terebrids, and 0.28 for
temperate species. Frequencies reported for other temper-
ate species are lower (VERMEIJ, 1978). The data presented
here and elsewhere (REIMCHEN, 1982; VERMEIJ, 1982a)
do not contradict conclusions about latitudinal predation
patterns, but they do show that shell breaking agents can
be locally intense in temperate as well as tropical gastro-
pod assemblages.
ACKNOWLEDGMENTS
I thank Director Cadet Hand and the staff at the Bodega
Marine Laboratory for providing space and use of the
fine facilities there. I also thank D. C. Edwards for a
critical and helpful review of the manuscript. This is a
contribution of the Center for Ecological Education and
Research.
JJo 18. Gelige, IMSS
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Predation pressure and gastropod foraging: a tropical-tem-
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MENGE, B. A. & J. LUBCHENCO. 1981. Community organi-
zation in temperate and tropical rocky intertidal habitats:
prey refuges in relation to consumer pressure gradients. Ecol.
Monogr. 51:429-450.
REIMCHEN, T. E. 1982. Shell size divergence in Littorina ma-
riae and L. obtusata and predation by crabs. Can. J. Zool.
60:687-695.
VERMEIJ, G. J. 1978. Biogeography and adaptation: patterns
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Rages
VERMEIJ, G. J. 1981. Predation through geological time: evi-
dence from gastropod shell repair. Science 214:1024-1028.
VERMEIL, G. J. 1982a. Environmental change and the evolu-
tionary history of the periwinkle Littorina littorea in North
America. Evolution 36:561-580.
VERMEIJ, G. J. 1982b. Gastropod shell form, repair, and
breakage in relation to predation by the crab Callapa. Mal-
acologia 23:1-12.
VERMEJJ, G. J., E. ZipsER & E. DUDLEY. 1980. Predation in
space and time: peeling and drilling in terebrid gastropods.
Paleobiology 6:352-364.
ZipSER, E. & G. J. VERMEIJ. 1978. Crushing behavior of
tropical and temperate crabs. J. Exp. Mar. Biol. Ecol. 31:
151-172.
The Veliger 26(2):116-118 (October 3, 1983)
THE VELIGER
© CMS, Inc., 1983
Morphological Divergence and Predator-Induced
Shell Repair in Alia carinata
(Gastropoda: Prosobranchia)
by
JULIA BERGMAN, JONATHAN B. GELLER, anp VICTOR CHOW
University of California Bodega Marine Laboratory, P.O. Box 247, Bodega Bay, California 94923
Abstract.
Morphological divergence of shell carina between protected harbor and exposed rocky
cove populations of Alia carinata (Hinds, 1844) at Bodega Bay was documented by assigning and
comparing keel ratings. The harbor population had a significantly higher frequency of highly keeled
individuals than the cove population. Shell-scar frequency data provide evidence that predation intensity
is greater in the harbor, and we suggest a relationship between morphological divergence and differential
predation pressure.
INTRODUCTION
POLYMORPHISM HAS BEEN observed in geographically sep-
arated populations of many gastropod species (e.g.,
KITCHING et al., 1966; SpiGHT, 1973; KITCHING &
Lockwoop, 1974; HELLER, 1976; VAN Marion, 1981;
REIMCHEN, 1982). Specific morphs often seem to be par-
ticularly well adapted to their local environment (e.g.,
KITCHING & LocKwoop, 1974). Compelling evidence for
this assertion comes from studies of the defensive mor-
phology of gastropods from sites with and without abun-
dant predators. Where predators such as durophagous
crabs are abundant, snail shells are thicker, more sculp-
tured, or have narrower apertures (KITCHING et al., 1966;
HUuGHEsS & ELNER, 1979; REIMCHEN, 1982), traits iden-
tified as adaptations primarily against predation (VER-
MEIJ, 1978). The major evidence supporting a causal re-
lationship between predator abundance and the presence
of armor is that armored shells are more resistant to
crushing forces (KITCHING ef al., 1966; KITCHING &
Lockwoop, 1974; CURREY & HUGHES, 1982).
Alia carinata (Hinds, 1844) (=Mitrella carinata) is a small
(<11 mm) columbellid gastropod found abundantly in the
low intertidal zone of northern California (see MORRIS et
al., 1980). Alia is especially common on the seagrasses
Phyllospadix scouler:i (Hooker) and P. torreyi (Watson) on
open rocky shores, while it is found on Zostera marina
(L.) on soft substrates. Preliminary observations indicated
that some specimens were noticeably more keeled at the
shoulder of the body whorl and that the outer apertural
lip was more crenulated (Figure 1). In this paper, we
document morphological divergence in A. carinata and
present evidence suggesting the divergence is a result of
differences in predation intensity between populations.
MATERIALS anpD METHODS
Our study sites were a sheltered, soft bottom harbor in
Bodega Bay, California, and a rocky cove (Horseshoe
Cove) just outside of Bodega Bay. Alia carinata were col-
lected at both sites by combing plants by hand from base
to tip in May, 1982. Shell length from base to apex and
greatest width perpendicular to the axis of coiling were
measured to the nearest 0.1 mm with vernier calipers. To
quantify extent of keeling, a standard set of morphotypes
was assembled which typified the range of keeling ob-
served in natural populations. Five individuals were se-
lected, ranked by extent of keeling, and assigned keel val-
ues of 1 (least keeled) to 5 (most keeled) (Figure 1). Snails
sampled from the harbor and the cove were assigned keel
ratings corresponding to the morphotype they most closely
resembled.
To quantify the frequency of shell scars, 475 harbor
snails and 343 cove snails, collected in July, 1982, were
examined with a binocular dissecting microscope under
low magnification. Any obscuring epibionts were gently
removed with a scalpel. Chipped outer lips, broken spires,
and jagged blemishes extensive enough to interrupt nor-
mal growth lines were considered predator-induced scars.
Eroded shell surfaces were not considered to be scars.
J. Bergman et al., 1983 Page 117
Figure 1
Dorsal (above) and apertural (below) views of Alia carinata showing extent of keeling. Keel ratings range from 1
(far left) to 5 (far right). Shell lengths of morphotypes vary from 7.4 to 8.1 mm.
ESI Ts significantly different in shell length. Although keeled
Harbor Alia carinata had a significantly greater width-to- morphotypes were present in both populations, keel rat-
length ratio (harbor: 0.526; cove: 0.469; Fi, 30.) = 224.10, ings were significantly greater for harbor Alia and highly
P < 0.01); however, harbor and cove samples were not keeled forms were absent from the cove habitat (Table 1).
Page 118
Table 1
Extent of keeling of Alia carinata collected from rocky cove
and soft-bottom harbor habitats. Distribution of keel rat-
ings differ significantly between the two study sites (Kol-
mogoroy-Smirnov Two Sample Test: DMAX = 0.7198;
P < 0.01).
Cove Alia Harbor Alia
Keel
rating Number Percent Number Percent
1 ews 67.24 13 9.70
2 42 24.14 13 9.70
3 15 8.62 48 35.82
4 0 0 42 31.35
5 0) 0) _18 13.43
Totals 174 100.00 134 100.00
The frequency of shell scars was significantly greater
in the harbor. Of 475 harbor Alia, 164 (35.6%) had scars.
Of 343 cove Alia, 51 (14.8%) were scarred (adjusted chi-
square = 23.16, P < 0.001).
DISCUSSION
Our results document shell-morphology divergence be-
tween Bodega harbor and rocky shore populations of Alia
carinata, and shell-scar data suggest that higher predation
rates in the harbor may account for this divergence. Al-
though we did not directly observe acts of predation on
Alia, shell scars are records of past predation attempts,
and shell-repair frequency is an indicator of predation
intensity on a population (see VERMEIJ, 1982; VERMEIJ
et al., 1981). Correlation of morphological patterns and
predation intensity is not sufficient evidence for the hy-
pothesis that local selection by predators has resulted in
interpopulation polymorphism. It must be shown that
variation in predator-induced mortality actually exists (z.e.,
a selective agent is acting), that present morphologies do
in fact confer resistance to predation, and that local mor-
phology has high heritability. Alternate explanations in
the absence of this information include ecophenotypic ef-
fects and differential mortality among uniformly and
widely dispersing larvae.
Our shell-scar data indicate that predation is a greater
hazard to harbor snails than those from the cove. Thus,
selection for defensive shell characteristics should be
stronger in the harbor. Because Alia carinata lays egg cap-
sules and has crawl-away larvae (D. Carlton, personal
communication), immigration from populations lacking
such selective pressure is unlikely. As a result, opportunity
for divergence is enhanced (CURREY & HUGHES, 1982).
Evidence that keeled snails are more resistant to crush-
ing is lacking. However, we have preliminary observa-
The Veliger, Vol. 26, No. 2
tions of prey selection by small Cancer antennarius (Stimp-
son), a predatory crab sympatric with both harbor and
cove Alia. In 12 2-h feeding trials in which six keeled and
six unkeeled snails were offered to starved C. antennarius,
30 unkeeled snails and 15 keeled snails were killed and
consumed. In addition, 14 unkeeled snails were damaged,
compared to only one keeled snail. These data are incon-
clusive, but suggest that keeled snails are less susceptible
to crushing predation. The evidence that morphological
divergence in Alia is related to predation is strong; how-
ever, ecophenotypic effects due to habitat differences such
as water temperature and velocity, time of aerial exposure,
and food availability cannot be ruled out.
ACKNOWLEDGMENTS
We thank Dr. Cadet Hand and the staff of the Bodega
Marine Laboratory for providing space and facilities for
this work. We are grateful to Robert A. Bergman for
kindly producing our photographs, and to Alberta Doyle
for friendship and encouragement.
LITERATURE CITED
Currey, J. D. & R. N. HuGHEs. 1982. Strength of the dog-
whelk Nucella lapillus and the winkle Littorina littorea from
different habitats. J. Anim. Ecol. 51:47-56.
HELLER, J. 1976. The effects of exposure and predation on
the shell of two British winkles. J. Zool. (Lond.) 179:201-
213.
HUGHES, R. N. & R. W. ELNER. 1979. Tactics of a predator,
Carcinus maenus, and morphological responses of the prey
Nucella lapillus. J. Anim. Ecol. 48:65-78.
KITCHING, J. A. & J. Lockwoop. 1974. Observations on shell
form and its ecological significance in thaisid gastropods of
the genus Lepsiella in New Zealand. Mar. Biol. 28:131-
144.
KITCHING, J. A., L. MuntTz & F. J. EBLING. 1966. The ecol-
ogy of Lough Ine. XV. The ecological significance of shell
and body forms in Nucella. J. Anim. Ecol. 28:331-341.
Morris, R. H., D. P. ABBoTT & E. C. HADERLIE. 1980. In-
tertidal invertebrates of California. Stanford University Press,
Stanford, Calif.-690 pp.
REIMCHEN, T. E. 1982. Shell size divergence in Littorina ma-
riae and L. obtusata and predation by crabs. Can. J. Zool.
60:687-695.
SpicHT, T. M. 1973. Ontogeny, environment, and shape of a
marine snail Thais lamellosa Gmelin. J. Exp. Mar. Biol.
Ecol. 28:215-228.
VAN Marion, P. 1981. Intra-population variation of the shell
of Littorina rudis (Maton) (Mollusca: Prosobranchia). J.
Moll. Stud. 47:99-107.
VERMEIL, G. J. 1978. Biogeography and adaptation: patterns
of marine life. Harvard University Press, Cambridge. 332
PP-
VERMEIJ, G. J. 1982. Gastropod shell form, breakage, and
repair in relation to predation by the crab Callapa. Mala-
cologia 23:1-12.
VERMEI, G. J., D. E. SCHINDEL & E. ZipseR. 1981. Predation
through geological time: evidence from gastropod shell re-
pair. Science 214:1024-1026.
The Veliger 26(2):119-123 (October 3, 1983)
- ‘THE VELIGER ©
© CMS, Inc., 1983
Thermal Effects on Some Mangrove Mollusks
HONG WOO KHOO anp ELEANOR CHIN
Zoology Department, National University of Singapore, Singapore
Abstract. The thermal tolerance to temperature of five species of tropical intertidal mollusks—
Coecella horsfield: horsfieldi, Diplodonta cumingu, Melongena pugilina, Mytilus viridis, and Terebralia
sulcata—were studied. Heat coma, acute lethal temperatures, and 6-h median tolerance limits were
used as measures of thermal tolerance. Each of these three indices produced a correlation between
intertidal location and the sensitivity of the species to thermal stress.
INTRODUCTION
THE USE OF COASTAL waters for cooling in electricity gen-
erating plants is increasing with greater demands for pow-
er. A number of these power plants are located near es-
tuaries and utilize estuarine water for cooling and
discharging heated water at temperatures about 10 to 15
C° above ambient. Although at the moment thermal pol-
lution is not critical, it is anticipated that in time to come,
with more powerful conventional as well as nuclear power
plants being built, thermal discharges could create prob-
lems to coastal ecosystems (NAYLOR, 1965).
In the tropics and in the South-east Asian countries
where inland water resources are limited, many of these
plants will be located on the coast and near mangroves.
Thermal changes in the mangrove environment could also
result from other sources, such as land development for
agriculture and industries, which could change the tem-
perature regime of surrounding waters.
Most studies on thermal effects have been conducted in
temperate regions (NAYLOR, 1965; HEDGPETH & GONOR,
1969). One of the few conducted in the tropical region of
South-east Asia was a study by MENASVETA (1976), who
evaluated the thermal effects on marine fishes of the Gulf
of Thailand.
Knowledge of thermal effects on the tropical mangrove
ecosystem and the associated organisms is very limited.
Our study contributes to this knowledge by investigating
the effects of heated water on five intertidal mollusks found
in the local mangrove mudflats of Singapore. The thermal
tolerance to increased temperature of the bivalves Coecella
horsfield: horsfieldi (Gray), Diplodonta cumingu Hanley,
and Mytilus viridis L., as well as the gastropods Melongena
pugilina (Born) and Terebralia sulcata (Born), were inves-
tigated. Hereafter, these species will be indicated by their
generic names.
MATERIALS ann METHODS
For each species, 12 batches of 10 individuals were placed
in 400-ml glass beakers containing well aerated seawater
(30 ppt) and placed in a thermostated water-bath that
was maintained at the test temperature. At hourly inter-
vals a batch of 10 was randomly selected, and the number
that survived was noted. Mortality was determined by
placing the treated animals back into seawater maintained
at room temperature (25°C) and then testing for sensitivity
responses of the foot or valve when the foot of the animal
was pricked with a needle (SOUTHWARD, 1958). Animals
that did not respond were considered dead.
The sensitivity test with the needle was also conducted
on the animals 5 min after treatment. The heat coma point
was defined as the lowest temperature at which no re-
sponse was elicited initially from the animal but on re-
turning the animal to room temperature full activity was
regained.
Treatment temperatures used in the experiments ranged
from 25 to 52.5°C at 2-3 C® intervals. These treatment
temperatures for each species are given in Table 1. The
animals were acclimated to room temperature (25°C) for
24 h before they were used in the experiments.
The survival curves for each species and at each treat-
ment temperature were obtained by plotting the number
alive against duration of treatment (Figure 1). After trans-
forming these curves into linear form by plotting the prob-
it of survival against the logarithm of treatment duration,
the 50% survival times were extracted and a sensitivity
curve for each species was drawn by plotting 50% survival
time against treatment temperature (Figure 2). From this,
the acute lethal temperature (ALT) was obtained. This
is the temperature at which 50% of the animals will die
instantaneously.
Another thermal tolerance index was determined from
The Veliger, Vol. 26, No. 2
Table 1
Treatment temperatures of five mangrove mollusks.
Page 120
Species
Coecella horsfieldi
horsfieldi 25 38 40.5
Diplodonta cumingu 25 33 35
Terebralia sulcata 25 38 40
Melongena pugilina 25 35 38.5
Mytilus viridis 25 35 Sod)
the 6-h temperature-mortality curves (,,TL,,). The 6-h
limit was chosen because most of these intertidal animals
are seldom submerged for more than 6 h per tidal cycle
in the natural environment.
RESULTS
Habitat of Test Organisms
Coecella, Diplodonta, and Terebralia are normally found
in the upper intertidal zone of the mangroves, whereas
Melongena and Mytilus are lower intertidal species.
Coecella is buried near the surface in sandbars located
in the tributaries draining the mangrove swamp. Dzplo-
donta is buried deeper in compact, moist mud, usually
located between the roots of the mangrove plants, and this
species is often found together with the peanut worm
Phascolosoma lurco (Selenka & de Man). Terebralia is found
along the muddy banks at the base of the mangrove plants
among the pneumatophores.
Melongena frequents moist, muddy habitats and areas
with large gravel and stones. Mytilus is found attached to
solid substrata, such as poles or concrete pillars, farther
away from the mangrove trees.
These intertidal mollusks are usually subjected to semi-
diurnal tides and are submerged and exposed twice a day.
The upper intertidal species are subjected to a longer du-
ration of desiccation and solar radiation than the lower
intertidal species. All are also subjected to fluctuating sa-
linities which ranged between 25 and 30 ppt, the former
at low tides and the latter at high tides.
Behavioral Responses to Heated Water
In general, all five species showed four phases of re-
sponse when exposed to increasing degrees of heated water.
At the lower temperature levels, the animals were active
and responded readily to needle pricks. Coecella and Dip-
lodonta showed vigorous burrowing movements of their
muscular foot. Specimens of Mytilus produced byssus for
attachment to the beaker and constantly opened and closed
their valves. Active crawling was observed in Melongena
and Terebralia. When pricked by a needle, both the bi-
valves and the gastropods showed their sensitivity by im-
mediate withdrawal of the foot or closure of the valves.
Treatment temperatures °C
46 47.5 50 52.5
41.5 43 45 47
45 47 49 51
40.5 41.5 42.5 45 47
39.5 41 43 45
Following this initial stage, a phase of lethargy was
observed. Occasional movements were noted and the an-
imals reacted slowly to needle pricks while still submerged
in the heated water. Copious secretion of mucus was ob-
served. After this phase the animals showed no reaction
when pricked. This occurred at higher temperatures, and
the animals apparently were in a state of heat coma. These
animals, however, regained their sensitivity to needle pricks
when they were transferred to room temperature seawa-
ter.
At the fourth and final phase, the animals were com-
pletely insensitive to needle pricks even after they were
transferred into room temperature water. The tissues of
these dead animals were tough and hard, whereas in the
previous comatose phase, the tissues were soft, flaccid, and
discolored.
Survival and Sensitivity to Heated Water
The survival curves for the five species are given in
Figure 1. The usual sigmoid survival patterns were ob-
served. The resulting sensitivity curves (Figure 2) showed
linear relationships between the 50% survival time and
the treatment temperature for all five species. Coecella
showed a slight deviation from the linear pattern.
Coecella and -Terebralia had the highest thermal toler-
ance followed by Melongena and Diplodonta. The least
tolerant was Mytilus.
The acute lethal temperature points (ALT), the tem-—
peratures at which 50% of the test animals would die
instantaneously, were obtained from the sensitivity curves
(Table 2). The ALT were highest, and similar, for Coe-
cella and Terebralia, about 50 and 49°C respectively. These
species were closely followed by Melongena and Diplodon-
ta with ALT of about 45°C. Mytilus had the lowest ALT,
about 43°C.
The heat coma temperatures (HCT) for the five species
are also given in Table 2. The highest HCT was observed
for Coecella (40.5°C) followed by Terebralia (40.0°C) and
Diplodonta (35°C). Melongena and Mytilus had the lowest
HCT (32°C).
The order of thermal tolerance measured by the HCT
is similar to that indicated by the ALT. A temperature
H. W. Khoo & E. Chin, 1983
=
\so°c \s7-5ec \ ere 45°C
& + Z
2 :
45°C \ ore MEE 40°C
2 + ae
0
(0) Tr UF Lr ul
D 0 2 i 6 8 12
c
=
2 ——- ——o a a «——. -——— re a—4
5 NY NE 25°C &
9 8} eae 43°C
64 + °.
6 Se Gs (c)
o 47 °
es] K NN a
ne}
|
2 | \agec Ne 45°C
iS ot Aeon r . 7 aS ——
= (0) 2 4 6 8 10 12
)
o
2
E
3
z
be oN
a Xx SS
\43ec << 395°C Ne
ot
ae G yO Vi
Nee
4
Treatment time in hours
Figure 1
Survival curves of five species of mangrove mollusks subjected to
different water temperatures. (a) Coecella horsfieldi horsfieldi, (b)
Diplodonta cumingu, (c) Terebralia sulcata, (d) Melongena pugi-
lina, (e) Mytilus viridis.
Page 121
Table 2
Thermal tolerance values of five mangrove
species of mollusks.
Heat tolerance indices (°C)
Heat Acute
coma lethal
Species point elles point
Coecella horsfieldi
horsfieldi 40.5 45.8 49.7
Terebralia sulcata 40.0 44.9 49.4
Diplodonta cumingi 35.0 41.5 45.1
Melongena pugilina 32.0 41.2 45.4
Mytilus viridis 32.0 39.1 43.0
difference between the two indices of about 10 C° was
observed for all five species.
The 6-h median tolerance limits, ,,0L,, (Table 2), ex-
tracted from the 6-h temperature-mortality curves (Figure
3), showed the same order of thermal tolerance as those
obtained from the other two indices. However, their tem-
perature values were halfway between the heat coma and
the acute lethal temperature points. The temperature dif-
ferences were almost the same for all species (4-5 C?).
DISCUSSION
Information on the temperature tolerance and response of
intertidal marine animals is of importance in assessing the
biological effects of thermal pollution and changed tem-
perature regimes in the aquatic environment. Studies on
a wide range of intertidal species are available (NAYLOR,
1965). However, benthic mollusks are especially suitable
for assessing the ecological effects of any thermal stress,
because, unlike the more mobile species such as fishes,
they are unable to move away from the affected areas.
Studies on mollusks are found in EVvANs (1947, 1948),
Davis (1960), SANDISON (1967), MISCALLEF & BANNISTER
(1967), HEDGPETH & GONOR (1969), and ANSELL (1973).
Studies on tropical species have been conducted by LEwIs
(1960, 1963, 1971) and ANSELL & TREVALLION (1969).
In many countries, changes of temperature in the man-
grove environment could result not only from direct ther-
mal discharges of electricity generating stations but also
from industrial heat waste, dams, irrigation practices, and
other land use activities such as housing and industrial
development nearby. In order to evaluate these changes
and their potential effects on the mangrove ecosystem, the
temperature tolerances of the resident organisms need to
be investigated first.
Our results showed that the tolerance of high temper-
ature by the five mollusk species is related to their vertical
distribution along the shore. All three heat-tolerance in-
dices indicate that the upper intertidal species, Coecella
and TJerebralia, were more tolerant than the lower inter-
Page 122
10 M. viridis
o
2 8 D. cumingii
<=
©
E 6 M.pugilina
©
>
S
= 4
7)
3e
°
wo 2
37 38 39 40 41 42 43
The Veliger, Vol. 26, No. 2
C.horsfieldii horsfieldii
T. sulcata
44 45 46 47 48 49 50
Treatment temperature °C
Figure 2
Temperature sensitivity curves of five species of mangrove mollusks. The 50% survival times (hours) were obtained
from log-probit transformation of the survival curves.
tidal species, such as Melongena and Mytilus. Diplodonta
is an exception: although it inhabits the upper intertidal,
it has lower heat tolerance than the above two upper in-
tertidal species. This is probably due to the fact that they
are adapted to live deeper in the mud substratum where
temperatures are normally lower than on the surface. A
similar correlation with vertical zonation has been shown
by other investigators (EVANS, 1948; BULLOCK, 1955;
GUNTER, 1957; SOUTHWARD, 1958; SANDISON, 1967).
They also have shown that thermal death points were
correlated with the order in which animals were zoned on
the shore.
Temperature °C
39 40 41 42
43 44 45 46 47
T.sulcata C.horsfieldii horsfieldii
M. pugilina
% Survival
M.viridis
D.cumingii
Figure 3
Six-hour temperature-survival curves of five species of mangrove mollusks. % survival on probit scale.
H. W. Khoo & E. Chin, 1983
Of the five species investigated, Mytilus consistently
showed the lowest heat-tolerance temperature indices.
Therefore, it should be the indicator species for evaluating
any thermal change, and their heat-tolerance tempera-
tures used as a basis for thermal pollution control of the
mangrove ecosystem.
The three heat-tolerance indices used in this study were
the heat coma temperature (HCT) following SOUTHWARD
(1958), the 6-h median tolerance limit (,,,TL,,) using the
usual bioassay methods, and the acute lethal temperature
(ALT) derived from the sensitivity curves. If comparison
of relative thermal tolerance among the species is re-
quired, it can be seen that any of the three indices could
be used.
Based on the above, then 31-—32°C should be the water
temperature criterion for the protection of the mangrove
ecosystem, and the decline in population size of Mytilus,
or its disappearance, should be one of the indications of
thermal stress to the ecosystem.
The temperature of the natural environment is between
28.5 and 30.5°C (THAM et al., 1970). Therefore, the ther-
mal stress temperature points of the species studied were
very close to the ambient temperature of their natural
environment. These tropical mangrove mollusks are living
very near to conditions of thermal stress. A small increase
of 2-3 C° in water temperature would be detrimental to
them and the mangrove ecosystem. Here, as well as else-
where, it seems that tropical organisms have low ranges
of temperature tolerance (MooreE, 1972).
In conclusion, it can be seen that in terms of thermal
stress, the mangrove is a fragile ecosystem. A slight tem-
perature increase definitely would affect it. In developing
the mangroves for aquaculture, agriculture, industrial or
other land use, careful consideration, therefore, should be
given to the changes in temperature regimes of the adja-
cent waters.
ACKNOWLEDGMENTS
We would like to thank Miss Tan H. B. for typing the
manuscript and Mrs. Yap O. Y. for drawing the figures.
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Tuam, A. K., H. W. KHoo & T. E. Cova. 1970. A study of
the plankton in Singapore waters in relation to the environ-
ment. Jn: J. C. Marr (ed.), The Kuroshio: a symposium on
the Japan Current. East-West Center Press. pp. 361-375.
The Veliger 26(2):124—127 (October 3, 1983)
THE VELIGER
© CMS, Inc., 1983
Barnacle Attachment on Live Nautilus:
Implications for Nautilus Growth Rate
by
NEIL H. LANDMAN
Department of Invertebrates, American Museum of Natural History,
Central Park West at 79th Street, New York, New York 10024
Abstract.
Attachment of the barnacle Chirona tenuis (1.8 cm in height) onto the mid-venter of a
juvenile Nautilus pompilius (10.7 cm in diameter) during its life permits observations on the secretory
reaction of the nautilus to the presence of the barnacle and provides an estimate of the growth rate of
N. pompilius in nature. The nautilus secreted a thick, multilayered, black film interleaved with aragonite
deposits in an attempt to overgrow the barnacle; the aragonite had a spherulitic-prismatic microstruc-
ture. The age of the barnacle provides a minimum estimate of the rate of growth of the last nautilus
whorl. Growth band counts on three wall plates average 680. If growth band formation is presumed
to be semidiurnal, based on field and experimental data for other barnacles, the age of the barnacle is
340 days and represents a minimum estimate of the rate of growth of the last nautilus whorl. Judging
from the spacing of chambers, about 16 chambers probably formed during this time yielding a minimum
average of about 21 days per chamber.
EPIZOA ON THE SHELLS of live Nautilus are not uncommon
and typically consist of serpulid polychaetes near the um-
bilicus or on the shell flanks and venter (SEILACHER, 1982).
The absence of more extensive premortal incrustation may
be explained by the mobile life style of Nautilus (STENZEL,
1964), its smooth shell covered with a thin, organic peri-
ostracum (BOTTJER, 1981), and possibly some antifouling
behavior. Barnacle attachment is rare but has been ob-
served on live N. belawensis from Palau (W. B. Saunders,
personal communication) and on live N. pompilius from
Fiji (B. A. Foster, personal communication).
While studying collections at the Museum of Compar-
ative Zoology, Harvard University, I discovered a small
shell of N. pompilius (M.C.Z. No. 138167), 10.7 cm in
diameter, with a large barnacle attached to its dorsum
(Figures 1, 2). The barnacle, 1.8 cm in height and 1.9 cm
in diameter, has been tentatively identified by B. A. Foster
from photographs as Chirona tenuis (Hoek). This species
lives in the Indo-West Pacific and elsewhere to depths of
500 m, approximating the maximum depth of N. pompi-
lius, and often occurs on the shells of gastropods (NEWMAN
& Ross, 1976, p. 50, and references therein). The nautilus
was collected off Golo Island, Mindoro, Philippines, and,
although other details of collection are not available, in-
crustation was evidently premortal as the nautilus was in
the process of overgrowing the barnacle. However, the
large size and position of the barnacle impeded further
growth of the nautilus and may have affected its swim-
ming and buoyancy capability. Aside from curiosity, this
occurrence permits two further inquiries: documentation
of the secretory reaction of the nautilus to the presence of
the barnacle, and estimation of the growth rate of Nautilus
in nature. The barnacle contains in its shell a record of
its growth. By deciphering this record, an estimate of the
age of the barnacle can be obtained which in turn permits
an estimate of the growth rate of the nautilus.
Secretory Reaction to the Barnacle
On the dorsal part of its shell, Nautilus secretes a black
layer or band presumably deposited by a portion of the
mantle fold (JouBIN, 1892). The black layer conforms to
the shell surface, dampening out growth lines and shell
irregularities. Epibionts such as serpulid worm tubes are
neatly covered with a slight thickening of the black de-
posit. The black deposit is itself continuously overlain by
an advancing layer of nacre as the animal grows, leaving
only the leading centimeter or so of the black layer free
of nacre (STENZEL, 1964). Thus, the black layer appar-
ently serves to enshroud epibionts and, as JOUBIN (1892)
suggested, to provide a more uniform surface for nacre
deposition.
N. H. Landman, 1983
In the nautilus specimen studied, these functions were
put to a severe test by the presence of the barnacle. The
black layer extended onto the shell flanks and overgrew
the lower edges of the barnacle walls. The black layer was
thick and multilayered and was interspersed with deposits
of aragonite which exhibited a botryoidal appearance un-
der low magnification (Figure 3). Under scanning electron
microscopy, these deposits revealed a spherulitic-prismatic
microstructure composed of radiating crystals about 70
um in length (Figure 4). This increase in secretory activity
near the barnacle was not matched by any shell thickening
at the apertural margin nor any reduction in the spacing
of the last chamber (Figure 5).
Barnacle Age and Nautilus Growth Rate
Using epibionts that grew during the lifetime of their
host to speculate about the growth rate of the host has
been attempted for extinct ammonites by SCHINDEWOLF
(1934). Although Nautilus is extant, information about its
growth rate in nature, especially in juvenile animals, is
sparse. DENTON & GILPIN-BROWN (1966), based on the-
oretical rates of gas-pressure build-up in newly formed
chambers of Nautilus macromphalus, inferred a constant
14-day periodicity between septal formation, a figure later
regarded as a minimum by COLLINS e¢ al. (1980). Nautilus
macromphalus maintained in aquaria have yielded esti-
mates of 1-4 months between septal formation (MARTIN
et al., 1978; WARD et al., 1981). The first estimates of the
growth rate of Nautilus in nature, based on the activity
ratio of two naturally occurring radionuclides incorporat-
ed into the shell during growth, yielded times of 25 and
75 days between septal deposition in two juvenile N. pom-
pilus 8.4 cm in diameter (COCHRAN et al., 1981).
Determination of the age of the barnacle attached to N.
pompilius provides another means of estimating the nat-
ural growth rate of Nautilus. The barnacle settled almost
exactly on the mid-line of the shell with its carinal plate
oriented in the adapical direction of nautilus growth. Sub-
sequent growth of the barnacle favored a bending toward
the left flank of the nautilus and the parietal plates are
shorter on this side. The basal disk is calcified and mea-
sures 1.9 cm in diameter. Below it on the shell surface,
approximately 28 asymetrically skewed concentric bands
radiate from the original attachment site.
The age of the barnacle yields a minimum estimate of
the rate of growth of the last nautilus whorl. The reasons
are outlined below.
(a) Depending on the position of the barnacle relative to
the aperture at the time of settlement, no more than
a full whorl of nautilus growth would have had to
elapse before reaching its present position at the time
of incipient overgrowth. According to SEILACHER
(1960), a barnacle will settle on an inclined substrate
with its carinal plate on top. Based on the orientation
of Chirona (see above) and the living position of Nau-
Page 125
tilus, the barnacle probably settled on the venter at
some distance behind the aperture, facing into the di-
rection of swimming. Therefore, less than a full whorl
of nautilus growth would have had to elapse before
reaching its present position.
Because the barnacle grew in both the adapical and
adoral directions of nautilus growth, the nautilus ac-
tually encountered it about 6 mm or a few degrees of
arc (~10°) adapical of its original attachment site.
Therefore, at most, a little less than a full whorl of
nautilus growth would have had to elapse.
(c) Because the details of collection are lacking, it is pos-
sible that the barnacle died some time before the nau-
tilus began to overgrow it. In this case, the age of the
barnacle would definitely be less than the time of for-
mation of the last whorl.
(b
wa
Determining the age of the barnacle presents its own
problems. The most reliable growth information is con-
tained in the form of internal growth bands visible in thin
sections of the parietes (BOURGET, 1980). Observations on
balanoideans reveal that growth bands are present in the
outer and inner layer (sheath) of the parietes and are wide
enough for counting (BOURGET, 1980). Interpretations of
growth-band periodicity are based almost exclusively on
field and laboratory experiments on intertidal and shallow
subtidal forms, principally Semzbalanus balanoides and El-
minius modestus. However, regardless of environmental
conditions, including total darkness and continuous im-
mersion, the production of growth bands is semidiurnal
(BOURGET & Crisp, 1975a, b; BOURGET, 1977, 1980). In
fact, BOURGET (1980) speculates that semidiurnal growth
band formation may be under endogenous control.
“1.) semidiurnal bands are observed subtidally in
newly metamorphosed animals; 2.) the production of
semidiurnal bands is immediate after metamorphosis;
3.) the production of semidiurnal bands cannot be
arrested in uniform conditions in the laboratory; 4.)
bands [are] observed in subtidal species (Bourget,
1977); and finally 5.) bands are also observed in the
deep-sea Bathylasma corraliforme sampled at a depth
of 7,000 m in Ross Sea, Antarctic.”
Based on these observations I will presume that the pro-
duction of growth bands in Chirona tenuis is semidiurnal.
The growth band record in C. tenuis was examined on
radial cross sections through three of the parietes. The
wall plates were sectioned, polished, etched for about 4
minutes with EDTA, and replicated with acetate. The
acetate peels were examined at 200X magnification with
transmitted light. Growth bands were counted on the in-
ner layer (sheath) of the parietes as suggested by BOURGET
(1980), and varied in width from 5 to 11 um (Figure 6).
Growth bands were counted by three independent observ-
ers, and the results are tabulated in Table 1. The counts
for all three parietes are similar and average 680 bands.
Presuming semidiurnal formation of growth bands, the
Page 126
The Veliger, Vol. 26, No. 2
Explanation of Figures 1 to 6
Figure 1. The barnacle Chirona tenuis attached to the shell of
Nautilus pompilius (MCZ No. 138167). Incrustation was pre-
mortal as the nautilus was in the process of overgrowing the
barnacle. The nautilus measures 10.7 cm in diameter; the bar-
nacle measures 1.8 cm in maximum height.
Figure 2. Close-up of Figure 1 showing the black layer deposited
on the wall of the barnacle. The carinal plate points in the
adapical direction of nautilus growth.
Figure 3. Botryoidal deposits of aragonite interlayered with the
black material (magnified 17.5X).
Figure 4. Spherulitic-prismatic microstructure of aragonite de-
posits in Figure 3.
Figure 5. X-ray photograph of nautilus (with barnacle removed)
showing regular spacing of septa.
Figure 6. Scanning electron micrograph of growth bands in Chz-
rona tenuis seen on an acetate replica of a radial cross section
through the inner layer (sheath) of a wall plate. Growth bands
measure 5 to 11 um.
N. H. Landman, 1983
Table 1
Counts of growth bands in three wall plates of
Chirona tenuis (Hoek).
Plate 1 Plate 2 Plate 3
709 665 680
682 669 684
687 647 673
683 686 684
709 656 660
706 696
Average 696.0 664.6 679.5
Standard deviation 13.30 14.67 12.13
Average all three plates 680.0
Standard deviation IS. 7/1
age of the barnacle is 340 days. As explained, this figure
represents a minimum estimate of the rate of growth of
the last nautilus whorl. Chambers in this specimen are
fairly regularly spaced and average 22° in angular arc
(Figure 5); approximately 16 chambers would have formed
during the growth of the last whorl. Therefore, the min-
imum average time of chamber formation for these 16
chambers is about 21 days. This figure is an average and
does not imply a constant periodicity. It compares favor-
ably with other estimates of natural growth rate based on
growth of the last 6-9 chambers in two juvenile N. pom-
pilius (COCHRAN et al., 1981).
ACKNOWLEDGMENTS
I thank K. Boss for arranging the loan of the specimen
and allowing me to section parts of the barnacle, B. A.
Foster for identifying the barnacle and suggesting useful
references, G. Harlow for identifying the calcareous de-
posits as aragonite, and E. Bourget for help and encour-
agement in interpreting the growth-band record. The
manuscript was critically reviewed by D. Collins and B.
Saunders, who made many helpful suggestions; R. Koest-
ler made the radiograph, B. Burns and B. Heimberg helped
in preparation of barnacle sections and counting growth
bands, and G. Rubic did the photographic reproductions;
A. Hkimi typed the manuscript.
Page 127
LITERATURE CITED
BoTTjer, D. J. 1981. Paleoecological implications of anti-
fouling adaptations in shelled marine molluscs. Geol. Soc.
Am. Abst. with Prog. 13(7):413.
BourGeET, E. 1977. Shell structure in sessile barnacles. Nat.
Can. 104:281-323.
BourGetT, E. 1980. Barnacle growth and its relationship to
environmental factors. In: D. C. Rhoads & R. A. Lutz (eds.),
Skeletal growth of aquatic organisms. Plenum Publishers.
pp. 469-491.
BourGEtT, E. & D. J. Crisp. 1975a. An analysis of the growth
bands and ridges of barnacle shell plates. J. Mar. Biol.
Assoc. U.K. 55:439-461.
BourcEt, E. & D. J. Crisp. 1975b. Factors affecting depo-
sition of the shell in Balanus balanoides (L.). J. Mar. Biol.
Assoc. U.K. 55:231-249.
CocuRaNn, J. K.,D. M. Rye & N. H. LANDMAN. 1981. Growth
rate and habitat of Nautilus pompilius inferred from radio-
active and stable isotope studies. Paleobiology 7(4):469-480.
Co.Luins, D., P. D. Warp & G. E. G. WESTERMANN. 1980.
Function of cameral water in Nautilus. Paleobiology 6:168-
NY.
DENTON, E. J. & J. B. GiLPIN-BROwWN. 1966. On the buoy-
ancy of the pearly Nautilus. J. Mar. Biol. Assoc. U.K. 46:
723-759.
Jousin, L. 1892. Recherches sur la coloration du tégument
chez les céphalopodes, 4 me partie, Gland sécrétant le vernis
noir chez le Nautile. Arch. Zool. Exper. Gén., Ser 2. 10:
319-324.
Martin, A. W., I. CATALA-STUCKI & P. D. WARD. 1978. The
growth rate and reproductive behavior of Nautilus macrom-
phalus. N. Jb. Geol. Palaont. Abh. 156:207-225.
Newman, W. A. & A. Ross. 1976. Revision of the balano-
morph barnacles; including a catalog of the species. San
Diego Soc. Natl. Hist. Mem. 9:1-108.
SCHINDEWOLF, O. H. 1934. Uber Epéken auf Cephalopoden-
Gehausen. Paldontol. Zeitschr. 16:15-31.
SEILACHER, A. 1960. Epizoans as keys to ammonoid ecology.
J. Paleontol. 34(1):189-193.
SEILACHER, A. 1982. Ammonite shells as habitats in the Po-
sidonia Shales of Holzmaden—floats or benthic islands? N.
Jb. Geol. Palaéont. Mh. 159(2):98-114.
STENZEL, H. B. 1964. Living Nautilus. In: R. C. Moore (ed.),
Treatise on invertebrate paleontology. Univ. Kansas Press
and Geol. Soc. Am., Lawrence, Kansas. part K:59-93.
WarbD, P., L. GREENWALD & Y. MAGNIER. 1981. The cham-
ber formation cycle in Nautilus macromphalus. Paleobiology
7(4):481-493.
The Veliger 26(2):128-135 (October 3, 1983)
THE VELIGER
© CMS, Inc., 1983
Distribution and Abundance of Caecum cornucopiae
(Gastropoda: Prosobranchia) on
Cladophora crystallina Mats in a Bahamian
Salt Water Lake
by
BETSY DAY
Department of Biology, University of Victoria,
Victoria, British Columbia V8W 2Y2, Canada
Abstract.
The minute gastropod Caecum cornucopiae (Gastropoda: Prosobranchia) was found in large
mats of the fine, filamentous green alga Cladophora crystallina in Sweetings Pond, a salt water lake on
Eleuthera Island, Bahamas. Caecum cornucopiae abundance decreased significantly between the top,
middle, and bottom algal layers (P < 0.05). From collections made over a four-week period, five stages
of shell growth were recognized. Stage correlated with aperture diameter (r = 0.92, n = 109) and was
used as a measure of relative age. Stage-frequency distribution varied between the top, middle, and
bottom layers of the C. crystallina mat. Stage-frequency distribution also varied with water depth, with
a higher percentage of Stages I and II (Guveniles) in deeper (7 m) water. Shallow water (0.5 m) contained
a more uniform stage distribution. Caecum cornucopiae was found in abundance in the gut of a small
brachyuran crab, and was also consumed by the fish Eucinostomus lefroyi.
INTRODUCTION
THE CAECIDAE IS A poorly known family of prosobranch
gastropods (Moore, 1972). Adults rarely exceed 3 mm in
length and are easily overlooked. Shell growth is unusual,
with immature stages passing through a planospiral pro-
toconch followed by a loose helix before maturation when
the shell becomes a gentle curve in one plane.
The literature on this family is scant and deals pri-
marily with taxonomy and distribution (WARMKE &
ALMODOVAR, 1963; SWEDMARK, 1964; ARNAUD & POIZAT,
1979). Moore (1972) presents systematic and ecological
notes on the Caecidae from St. Croix, U.S. Virgin Islands.
He reports that Caecum cornucopiae Carpenter, 1858, is
a tropical, stenohaline species found near coral reefs and
in lagoons where salinity does not decrease during fresh-
water runoff. This species has been found in the Bahamas,
southern Florida, the western Caribbean, Puerto Rico,
Jamaica, and the Lesser Antilles.
This report describes the habitat, distribution, and
predators of a population of Caecum cornucopiae. Obser-
vations on the stages of shell growth are also included.
MATERIALS anpD METHODS
Description of Study Site
Sweetings Pond (Figure 1) is an enclosed, salt water
lake measuring 1.5 X 0.75 km, with a maximum depth of
approximately 16 m. It is presumed to be connected to the
Caribbean Sea through an underground cavern. Tidal
amplitude in the pond is less than 10 cm. Ranges for
Figure 1
Location of the study site, Sweetings Pond, Eleuthera, Bahamas. Numbers in small-scale (bottom) map refer to
sampling stations.
B. Day, 1983 Page 129
76°30’
Atlantic Ocean
{Harbour Island
Atlantic
Ocean
overnor'’s Harbour
Eleuthera Island
SOUTH
AMERICA
-——— Rock Sound
CENTRAL 1000 Km
AMERICA
Caribbean Sea
Caribbean Sea
Magnetic
North
Sweetings Pond
----dirt road
Page 130
temperature (24-28°C), dissolved oxygen (6-7 mg/l), and
salinity (36-38 ppt), all are similar to those of the Carib-
bean Sea. Currents are insignificant, although turbidity
during the spring of 1982 was high: a Secchi disk held
horizontally was not visible beyond 441 cm.
Mats of Cladophora crystallina (TAYLOR, 1960) were
found at depths from 1 to 6 m around the perimeter of
the pond, but their areal coverage varied. The alga often
formed a solid mat up to 114 cm thick between 3 and 5
m, and occurred as patches in shallower and deeper lo-
cations.
Three stations were sampled (Figure 1). Station 1 was
located in the middle of approximately a one-half hectare
of algal mat, interrupted by occasional patches of sediment
2-3 m in diameter. Station 1 was over 5 m away from
any sediment, and it is assumed that sediment fauna did
not interact with mat fauna at Station 1; water depth was
2.5 m. Stations 2 and 3 were within 0.5 m of the sediment
on patches of C. crystallina covering less than 3 m?, at
depths of 7 and 0.5 m, respectively.
Methods
Temperature was measured in and above the mat of
Cladophora crystallina at Station 1 (+1°C). Dissolved oxy-
gen was determined using a Hach field kit (model OX-
2P, with a precision of 1 mg/1) at the bottom, middle, and
top of the algal mat, as well as 1.5 m above the mat.
The shell-aperture diameter of 109 Caecum cornucopiae
was measured with an ocular micrometer to the nearest
0.01 mm. Aperture diameter was thought to reflect rela-
tive age as it must increase as the animal grows. Five
stages of shell formation were recognized based on pro-
toconch presence or loss, the amount of helical coiling,
and the loss of posterior shell sections.
The stage-frequency distribution of Caecum cornucopiae
at the top, middle, and bottom of the algal mat was ex-
amined at Station 1. Each layer was sampled at three sites,
with six replicates per site. Because sampling was destruc-
tive to the mat it was impossible to sample all three layers
at one site. All sampling occurred within a 3-m radius of
the Station 1 buoy. Sites were located adjacent to or be-
neath (for the middle and bottom layers) a % m? quadrat
that was released at the water surface and allowed to drift
haphazardly to the mat. Thickness of the algal mat at
each sampling site was measured prior to sampling. Sam-
ples were collected by holding the halves of a tea ball 50
mm apart and pressing them into a vertical wall of algae
to a depth equal to the tea ball diameter. The tea ball
halves were then brought together enclosing a cylinder of
algae with a volume of 61.3 cc. Each sample was sorted
under a dissecting microscope for enumeration of C. cor-
nucopiae stages, as well as for the identification and enu-
meration of all other species. Crustaceans were not iden-
tified further due to taxonomic difficulties. Because the
algal mat became compressed with increasing thickness
due to the weight of overlying layers, displacement vol-
The Veliger, Vol. 26, No. 2
umes of all algal samples were recorded after the algae
had been blotted dry. This allowed standardization of all
enumerations to numbers per volume of Cladophora crys-
tallina.
At Stations 2 and 3, a handful of top-layer algae was
collected for stage-frequency comparisons of Caecum cor-
nucopiae at different water depths. Algae were sorted until
the first 60 or more individuals were assigned to stage
classes.
Gut contents of large, algal mat fauna, as well as those
of three species of fish seen over the mats, were examined
to determine to what extent any of these species was uti-
lizing Caecum cornucopiae as a food source.
RESULTS
All physical measures were collected between 1000 and
1600 h. Temperature above and within the Cladophora
crystallina mat ranged between 26 and 27°C. Dissolved
oxygen was 8 mg/] in the surface layer of the mat, 5 mg/1
in the middle, and less than 3 mg/] (the minimum con-
centration accurately detectable with the Hach kit) in the
bottom layer. The water above the C. crystallina mat con-
tained 7 mg/] dissolved oxygen.
Five stages of shell formation were recognized (Figures
2-6). Stage I, the protoconch, exhibits planospiral coiling
(Figures 2a, b). Stage II begins when the shell completes
roughly a 60° curve to the left, away from the plane con-
taining the planospiral protoconch (Figures 3a, b). After
the loss of the protoconch through breakage, individuals
were termed Stage III (Figure 4). Stage III shells are
curved through at least 60°, and lie in one plane. As growth
continues the shell begins to resemble a loosely wound
helix. Stage IV shells possess this helical shell (Figure 5)
resembling a cornucopia. When the Stage IV posterior
curves break off, Stage V is attained (Figure 6). Stage V
shells are gently curved, and as with Stages I and III, lie
in one plane. Length and aperture diameter in Stage V
are up to five times greater than in Stage I. Stage V spec-
imens exhibit polymorphism in that some have parallel
rows of white spots on the otherwise amber-brown shell.
Animals with white spots were four times more abundant
on the surface layer of the alga at all stations (7 individ-
uals without spots, 32 with spots). In the middle of the
mat, 37 were plain and 3 were spotted, while in the bot-
tom algal layer neither form was obviously dominant (5
without spots, 4 with spots).
Caecum cornucopiae attains a maximum length of 2.5
mm. The protoconch is white in color, with later stages
becoming progressively browner as the shell thickens. The
proboscis, head region, and tentacles have variable white
areas.
Pearson’s product moment correlation coefficient was
calculated for the 109 measures of aperture diameter and
stage, with a resultant r = 0.92. The equation
y =0.11x + 0.02
B. Day, 1983
Page 131
Explanation of Figures 2 to 6
Figures 2-6. Scanning electron micrographs of the stages of shell Figure 3b. Stage II, x 28.
growth in Caecum cornucopiae. Figure 4. Stage III, x 28.
EUGUEe Zan Sage 1b SG: Figure 5. Stage IV, X 28.
Figure 2b. Stage I, X 28.
Figure 3a
. Stage II, X 119.
Figure 6. Stage V, X 28.
Raceway
eo)
oO
Aperture diameter (mm)
1 2
The Veliger, Vol. 26, No. 2
3 4 5
Stage
Figure 7
Stage of shell formation vs. aperture diameter for Caecum cornucopiae. Bars represent 1 standard deviation around
the mean.
where x is shell stage and y represents aperture diameter,
may be used to describe this relationship (Figure 7). Be-
cause one-way, unequal-N ANOVA’s showed each stage
class to be significantly different from its adjacent classes
(P = 0.01), all distribution studies of Caecum cornucopiae
utilized stage instead of aperture diameter as a measure
of relative age.
Table 1 presents abundance data from Station 1. Anal-
ysis of variance within each layer found the three sites
where the top algal layer was sampled to be significantly
different from one another (P = 0.025), whereas signifi-
cance was not found in either the middle (P = 0.683) or
bottom layers (P = 0.492).
Abundance of Caecum cornucopiae decreased signifi-
cantly at Station 1 (P < 0.05) with increasing depth in
the algal mat (Table 2). Spirorbid polychaetes, juveniles
of the bivalve Pinctada radiata, and an unidentifiable ju-
venile bivalve showed similar zonation. Thickness of the
mat of Cladophora crystallina varied between 59 and 67
cm at Station 1: there is no evidence this influenced the
distribution of C. cornucopiae.
One of the 18 replicates collected from the bottom of
the algal mat contained 26 Caecum cornucopiae whereas
the mean of the other 17 replicates was 1.35 animals per
sample (standard deviation = 1.32). When standardized
to number per 1 ml of alga, the anomalous replicate con-
tained 16 times more C. cornucopiae than the mean of the
other 17 replicates. This replicate is not included in Table
2 (** Table 2).
Table 1
Abundance of Caecum cornucopiae at Station 1. Three sites
(n = 6) were sampled at each algal layer. Probability val-
ues are presented following ANOVA testing to determine
intra-layer variation.
Abundance
Algal mat layer (mean + 1 SD)
Top 266.3 + 175.1
121.2 + 58.9 0.025
390.6 + 172.3
67.7 + 24.6
Wo 2 ZVD 0.683
65.0 + 8.4
Bottom 12.2 = 9.3
26.6 + 50.7 0.492
58+9.7
Probability
Middle
B. Day, 1983
Page 133
Table 2
Abundance data (mean + SD) from the surface, middle,
and bottom of the Cladophora crystallina mat at Station 1.
Samples have been standardized to number per 1 ml of
alga (displacement volume). * indicates abundances be-
tween adjacent layers are significantly different within
that species (P < 0.05) (n = 18, except for **, where n =
17; see text).
Top Middle Bottom
Species layer layer layer
Caecum cornucopiae 23D 32 UID" TWO ae BS Q as Bie Me
Spirorbid polychaetes AS ae Gl — 29) ae hh 2 ae NS
Pinctada radiata G3 as RO" 83} ae G+ @ se 7/3
Juvenile bivalve Dac iil 0.5 a 2O- 0
Leptosynapta sp. 244 Oss) as O.7/ 0
Ophiuroid 0.5 + 1.2 0 0
Flatworm 7, az (6) 0 0
Anemone OL as 1.7 0 0
Nudibranch 2) ae 1.7 0 0
Hydroid O39 a3 1.2 0 (0)
Polymesoda maritima O39) ax; tle 0 0.5 + 2.4
Eurythoe sp. OD 212 O,8:a5 IZ 0
Larvae 0.3 + 1.2 0 0
The stage-frequency distribution at Station 1 also var-
ied with depth within the mat of Cladophora crystallina
(Figure 8). The percentages of the populations in Stage I
at the surface, middle, and bottom of the algal mat were
approximately the same. The same trend was seen for
% of pop.
Stage IV. The percentage in Stage II decreased with depth.
Stage III animals were most abundant in the bottom algal
layer where they were the majority of the population, and
were least abundant in the middle of the mat. Animals in
Stage V showed a normal distribution with increasing
depth in the mat.
The stage-frequency distributions of Caecum cornuco-
piae on the mat surface at Stations 1, 2, and 3 were varied
(Figure 9). Station 1 showed a skewed distribution with
the population maximum at Stage II. Station 2 seemed to
contain a younger C. cornucopiae population, with over
70% in Stages I and II. Station 3 showed a more uniform
population structure, but with few in Stage I.
A small brachyuran crab, the mottled mojarra Euci-
nostomus lefroyi, and the scrawled cowfish, Lactophrys
quadricornis, were found to consume Caecum cornucopiae.
Of the 20 crabs examined, 19 had guts with partially
digested food, and all of these contained either shells or
opercula of C. cornucopiae. The guts of 25 E. lefroyi col-
lected during daylight hours were examined; 48% con-
tained C. cornucopiae shells (R. Aronson, personal com-
munication). The maximum number of shells in 1 gut
was 40, with an average of 5.9; 99.4% of the shells were
located in the intestine, suggesting that predation occurred
at night. Caecum cornucopiae comprised less than 5% of
the gut-content volume of one Lactophrys quadricornis.
DISCUSSION
The stages of growth herein described were determined
by two criteria, loss of previous shell growth and shell
shape. It is assumed that loss of previous growth occurs
123 4 5 123 4 5 7 2S as
Surface of Middle of Bottom of
algae algae algae
Stage
Figure 8
Stage-frequency distribution of Caecum cornucopiae from the surface, middle, and bottom layers of the Cladophora
crystallina mat at Station 1.
Page 134
% of pop.
123 4 5 1 2 3 4 °5 1284 8
Station 1 Station 2 Station 3
(2.5 m) (7.0 m) (0.5 m)
Stage
Figure 9
Stage-frequency distribution of Caecum cornucopiae in the surface layer of the Cladophora crystallina mat at different
locations within Sweetings Pond. Water depths are presented below each station designation. Refer to Figure 1
The Veliger, Vol. 26, No. 2
for station locations.
due to breakage. Predatory attempts are not thought to be
a primary cause of breakage because it is unlikely that all
individuals would experience such attempts. Elements
causing breakage in the Cladophora crystallina environ-
ment have not been recognized.
The ability to utilize aperture diameter as a measure
of relative age allowed a great deal of information to be
assimilated quickly and accurately. Variation in the range
of aperture diameters in each stage was expected because
growth is a continuous process (Figure 7).
The pattern of variation in the stage-frequency distri-
bution within the algal mat (Figure 8) is not understood,
and may reflect natural variation within the population
and/or undocumented movement patterns. Abundance de-
creased with mat depth, probably as a result of decreased
oxygen. However, other potentially limiting factors in-
clude the presence of hydrogen sulfide, predation, and food
resources, all of which presumably change with algal mat
depth.
The distribution of Caecum cornucopiae seems patchy.
First, analysis of variance of the top algal layer at Station
1 (Table 1) showed the three sites to contain significantly
different abundances. Second, the anomalous replicate col-
lected in the bottom layer of the Cladophora crystallina mat
at Station 1 contained 16 times more Caecum cornucopiae
than the mean of the other 17 standardized replicates.
There are two possible explanations: clumping and sam-
pling error. Sampling error could occur if a piece of C.
crystallina from the surface layer was carried to the bottom
during sampling. However, the other fauna in the sample,
Pinctada radiata and spirorbid polychaetes, were found in
densities comparable to the other bottom replicates. It is
suggested, therefore, that in this sample the C. cornucopiae
were clumped around a potentially beneficial resource.
Variation in stage composition with the water depth at
which the population was found (Figure 9) suggests two
things. First, recruitment may occur earlier in shallow
areas. At 7 m, 40% of the population is in Stage I, whereas
at 2.5 and 0.5 m, 18% and 8% percent are in Stage I,
respectively. Variation in water temperature and/or in-
solation are possible causes. Second, the stage-frequency
distribution representing the population found at 0.5 m
suggests decreased post-Stage I mortality as compared to
populations at 2.5 and 7 m. Observations revealed the lack
of Eucinostomus lefroy., Lactophrys quadricornis, and the
brachyuran crab, predators of Caecum cornucopiae, in
shallow water. Such absence might account for the ob-
served distribution.
The presence of Stage V Caecum cornucopiae on muslin
bags at Station 4 at least 3 m from any Cladophora crys-
tallina suggested horizontal movement on or in the sedi-
ment. However, the distribution of C. cornucopiae in the
sediment was not determined.
Five of the six samples reported in Figures 8 and 9
show Stage IV individuals composing less than 10% of the
population. Although the cause for this distribution is not
known, it may represent a break between reproductive
classes, or widespread mortality during development.
The dense population of Caecum cornucopiae on mats
of Cladophora crystallina in Sweetings Pond may have a
B. Day, 1983
significant effect on the alga by consuming epiphytic ma-
terial or the alga itself. Because of its abundance, C. cornu-
copiae may be an important link in the pond’s food web,
but only further study will reveal the role that C. cornu-
copiae assumes in this ecosystem.
ACKNOWLEDGMENTS
My thanks to Richard B. Aronson who introduced me to
Sweetings Pond and who also collected the Eucinostomus
lefroy: gut-content data. Caecum cornucopiae was identified
by T. Abbott, and C. J. Bird identified Cladophora crys-
tallina; H. R. Baker, R. D. Burke, L. M. Coon, D. V.
Ellis, P. A. Gee, L. A. Taylor, and an anonymous review-
er contributed to the development of the manuscript. This
study was supported by National Science Foundation
Page 135
Grant DEB-8114684 and a grant from the Richmond
Fund of Harvard University, both to Richard B. Aronson.
LITERATURE CITED
ARNAUD, P. M. & C. PoizatT. 1979. Donnés écologiques sur
des Caecidae (Gasteropodes Prosobranches) du Golfe de
Marseille. Malacologia 18:319-326.
Moore, D. R. 1972. Ecological and systematic notes on Cae-
cidae from St. Croix, U.S. Virgin Islands. Bull. Mar. Sci.
22:881-899.
SWEDMARK, B. 1964. The interstitial fauna of marine sand.
Biol. Rev. 39:1-42.
TayLtor, W. 1960. Marine algae of the eastern tropical and
subtropical coasts of the Americas. University of Michigan
Press, Ann Arbor, Michigan. xii + 870 pp.
WarMKE, G. L. & L. R. ALMoDOvAR. 1963. Some associa-
tions of marine mollusks and algae in Puerto Rico. Mala-
cologia 1:163-177.
The Veliger 26(2):136-138 (October 3, 1983)
THE VELIGER
© CMS, Inc., 1983
The Bermudan and Caribbean Sacoglossan Mollusk
Elysia flava Verrill Now Recorded
from the Greek Aegean Sea
T. E. THOMPSON
Zoology Department, University of Bristol, England
Abstract. This Bermudan type has now been recorded from Tenerife, Jerba (Tunisia), the west
coast of the Greek Aegean island of Evia, and the north shore of the Gulf of Corinth. It represents a
new record for the Mediterranean Sea and a range-extension of many thousands of kilometers.
INTRODUCTION
ONE OF THE LEAST known sacoglossans (=ascoglossans)
of the Atlantic Ocean, Elysia flava Verrill, 1901, was first
described from the shore at Castle Harbour, Bermuda. It
was distinct by virtue of its short, non-papillate rhino-
phores, white tuberculate parapodial rims, and the white
papillae inside the parapodia. VERRILL (1901) studied an
unknown number of specimens, up to 18 mm in length;
he recorded it as “rare.” In 1977 my observations on Ja-
maican sacoglossans were published, including a descrip-
tion of two specimens of EF. flava, one from the north of
the island, the other from the south (THOMPSON, 1977).
These were the first reports of this distinctive species since
Verrill’s type-description.
Since that time, a further record of EF. flava has come
from ORTEA (1982) who described two specimens, 11 and
13 mm in length, from Tenerife in the Canary Islands;
this was the first citation from the eastern Atlantic.
Sublittoral collections in Greek waters in the summer
of 1982 have yielded three further specimens, extending
the known range by thousands of kilometers. At the same
time, Dr. Philippe Bouchet obtained similar material from
the coast near Jerba (sometimes written Djerba), on the
Tunisian shores of the Mediterranean Sea. The depth
range was 1-8 m. The opportunity was taken to re-in-
vestigate the internal anatomy, especially the sexual or-
gans and the radula.
Many other Mediterranean Elysia species have been
described and illustrated by SCHMEKEL & PORTMANN
(1982), and a taxonomic review is being prepared by Dr.
Bouchet.
DESCRIPTION
Material. Two specimens were found in subtidal shallows
(to 2 m) 4 km to the south of Amarynthos, on the west
coast of the Aegean Island of Evia, 23 July 1982 (length
15 mm) and 17 August 1982 (length 10 mm). Another
specimen was found in 1 m of water, near Eratini on the
north shore of the Gulf of Corinth, 30 July 1982 (11 mm).
All were found under loose stones.
External features. The overall color is pale yellowish
green, through which the dark green lobes of the digestive
gland can be discerned. There is a little crimson speckling
Figure 1
Elysia flava Verrill. A, Dorsal view from life of a 15-mm specimen from Evia, July, 1982. B, Ventral view of the
head of the same. C, Enlarged view of the parapodial rim. D, Radular tooth, 34 um in length, of a 10-mm specimen
from Evia, August, 1982, examined in polyvinyl lactophenol.
T. E. Thompson, 1983 Page 137
cardiac /.
prominence}.
5mm
papilla
white rim
pale zone
igestive gland
cusp
Page 138
on the epidermis of the head, and over much of the rest
of the body, both inside and outside the parapodial lobes.
The parapodial rim is white and bears numerous blunt
papillae; similar papillae can be found inside the para-
podia, sparsely distributed. The rhinophores are short and
bear a few large white blotches. The head is pale yellow
in color, slightly bilobed anteriorly. The propodium is
markedly bilobed. There are no gills (blood-engorged folds
of the epithelium) inside the parapodia.
Anatomy. The radula of the 10-mm specimen was ex-
amined in polyvinyl lactophenol. The formula was 19 X
0.1.0; all the teeth were smooth. The 15-mm specimen
was serially sectioned. The ovotestis was filled with ripe
The Veliger, Vol. 26, No. 2
eggs and sperm. No spawn was found either in the field
or the laboratory.
LITERATURE CITED
OrTEA, J. 1982. Moluscos opistobranquios de las islas Can-
arias. Primera parte: Ascoglosos. Bol. Inst. Espa. Oceanogr.
6:192-213.
SCHMEKEL, L. & A. PORTMANN. 1982. Opisthobranchia des
Mittelmeeres Nudibranchia und Sacoglossa. Springer-Ver-
lag, Berlin. x + 410 pp.
TuHompson, T. E. 1977. Jamaican opisthobranch molluscs. I.
J. Moll. Stud. 43:93-140.
VERRILL, A. E. 1901. Additions to the fauna of the Bermudas
from the Yale Expedition of 1901 with notes on other species.
Trans. Conn. Acad. Sci. 11(1):15-62.
The Veliger 26(2):139-141 (October 3, 1983)
THE VELIGER
© CMS, Inc., 1983
Do Oystercatchers Influence Limpet Shell Shape?
by
P. A. R. HOCKEY' anp G. M. BRANCH?
‘Percy FitzPatrick Institute of African Ornithology, University of Cape Town,
Rondebosch 7700, South Africa
2 Department of Zoology, University of Cape Town,
Rondebosch 7700, South Africa
Abstract.
The Black African Oystercatcher, Haematopus moquini, most often attacks limpets at the
posterior margin. When feeding on Patella granularis, it preferentially attacks individuals that are pear-
shaped rather than elliptical, presumably because the posterior margin is more easily distinguished in
such shells. Patella granularis is more pear-shaped in habitats inaccessible to oystercatchers and in
localities lacking oystercatchers, indicating that the selective effect of oystercatchers is sufficient to alter
the phenotypic shell shape and probably also the genotypic composition of limpet populations preyed
upon.
INTRODUCTION
VARIATIONS IN THE intensity of predation on gastropod
populations by fish and invertebrates can lead to regional
adaptations in shell morphology (EBLING ef al., 1964;
VERMEIJ, 1978; PALMER, 1979), but very little is known
about predation by birds in relation to shell form (VER-
MEIJ, 1978; but see HARTWICK, 1981) in spite of the fact
that birds may have a substantial impact on limpet pop-
ulations (FRANK, 1982).
Observations on shell remains lead to the conclusion
that African Black Oystercatchers, Haematopus moquini,
preferentially attack limpets (Patella spp.) at the posterior
margin of the shell, and make “correct” attack decisions
most consistently on limpet species whose posterior and
anterior sectors are clearly distinguishable, such as Patella
cochlear (HOCKEY, 1981). The dominant limpet in the diet
of the African Black Oystercatcher is P. granularis, an
elliptically shaped species of the mid- and upper-intertidal
regions of southern Africa (Hockey & Underhill, MS).
There is no specific orientation of P. granularis on rock
faces (unpublished data); therefore, posterior attack is
presumed to be choice by the birds. The proportions of
attacks delivered by oystercatchers at the posterior, mid-
dle, and anterior sectors of the shells of this species are
respectively, 49.3%, 12.1%, and 38.6% (n = 487) (HOCKEY,
1981).
Presumably, limpets that are approached from behind
by oystercatchers have less warning of the attack and are,
therefore, less likely to clamp down prior to attack. If
African Black Oystercatchers are most successful when
attacking limpets posteriorly, it would be advantageous,
when dealing with a uniformly elliptical species, to attack
those individuals which are most pear-shaped, and hence
have most recognizable posterior ends. If this strategy is
adopted, then two testable hypotheses emerge concerning
shell shape within populations of P. granularis.
Firstly, limpets in regions where there are no oyster-
catchers will be more pear-shaped than limpets in
regions where oystercatchers occur, where pear-shaped
limpets will have been removed preferentially.
Secondly, within regions where oystercatchers occur,
limpets in inaccessible sites (vertical rock faces) will
be more pear-shaped than accessible limpets, but, as-
suming genetic control of shell shape, more elliptical
than limpets in areas where there are no oystercatch-
ers.
METHODS
Random samples of P. granularis were collected at five
localities in South Africa and Namibia within the range
of the African Black Oystercatcher. Three types of limpets
were distinguished: those eaten by oystercatchers (shells
collected from chick “‘middens’”’); those living on rocks ac-
cessible to oystercatchers; and those living on rocks inac-
cessible to oystercatchers (vertical faces). Oystercatchers
do not deposit all the shells that they remove in middens,
but chick middens are the most reliable source of large
quantities of shells that definitely have been preyed on by
oystercatchers. Additionally, collections were made at sev-
Page 140
The Veliger, Vol. 26, No. 2
Table 1
Mean shell uniformity indexes (SUIs) + SD for 17 samples of Patella granularis from southern Africa.
Mean length
Type of limpet population Sampling location (mm) + SD Mean SUI + SD
Depredated by oystercatchers Malgas Is. (33°03’S; 17°55'E) 38 + 6 0.91 + 0.03
Possession Is. (27°01'S; 15°12’E) BV) a2 §) 0.92 + 0.06
Jutten Is. (33°05’'S; 17°57'E) 45+11 0.92 + 0.04
Overall mean 0.92 + 0.05
Accessible to oystercatchers Malgas Is. 47 +8 0.95 + 0.03
Owen Is. (29°16’S; 16°52’E) 38 +4 0.94 + 0.04
Jutten Is. 3645 0.93 + 0.03
Cape Columbine (32°50'S; 17°50’E) VY x= 3 0.94 + 0.04
Overall mean 0.94 + 0.04
Inaccessible to oystercatchers Malgas Is. 3645 0.92 + 0.04
Jutten Is. 3144 0.91 + 0.04
Cape Columbine 2443 0.93 + 0.06
Overall mean 0.92 + 0.04
Predator-free Swakop River (22°41’S; 14°31’E) 30 + 6 0.86 + 0.08
Mile 105 (21°25'S; 13°50’E) 50+6 0.87 + 0.04
Terrace Bay (20°00’S; 13°00’E) 31+6 0.93 + 0.03
Mowe Bay (19°20'S; 12°43’E) 37/ 22 6 0.90 + 0.05
Rocky Point (19°01'S; 12°29’E) 34+6 0.92 + 0.04
Angra Fria (18°20'S; 11°58’E) 29 +6 0.86 + 0.09
Kunene River (17°20'S; 11°50’E) A) se 7/ 0.88 + 0.07
Overall mean 0.89 + 0.06
en sites in northern Namibia which are free from oyster-
catcher predation. Each sample comprised 30 individuals
of various sizes, but the limpets selected for measurement
fell within the size range eaten by oystercatchers (Hockey
& Underhill, MS). All samples were taken from shores
with high wave action.
For each limpet, a Shell Uniformity Index (SUI) was
calculated. The SUI was the ratio of the width of the shell
one third of the way from the anterior edge to the width
one third of the way from the posterior edge: thus, indi-
viduals with SUIs close to unity were more elliptical than
those with lower SUIs. Shell widths were measured with
vernier calipers to the nearest 0.5 mm. For each sample
a mean + SD was calculated, and mean SUIs were com-
pared between samples using a t-test. Data (SUIs) were
normalized using an arc sin transformation (Y’ =
sin-'(VY)) to allow statistical comparison. Limpet length
(maximum, in mm) also was measured.
To test whether SUI is influenced by wave action in-
dependently of predation, two samples of 30 inaccessible
limpets were collected at Froggy Pond (34°12’S; 18°28’E).
One sample was taken from an area exposed to heavy
wave action and the other from a sheltered area. These
two samples contained a wide range of sizes and also were
used to test whether SUI is related to size.
RESULTS
Shell Uniformity Indexes ranged from 0.86 + 0.04 to 0.95
+ 0.03 (Table 1). T-tests indicated the following differ-
ences between populations of limpets in different regions
and sites.
(a) The mean SUI for all limpets in predator-free pop-
ulations (0.89 + 0.06, n = 210) was significantly less (t =
6.89, P < 0.001) than for limpets from all depredated
populations (0.93 + 0.04, n = 300).
(b) Inaccessible limpets had a significantly lower SUI
than accessible limpets at Malgas Island (t = 3.16, P <
0.01) and at Jutten Island (t = 2.27, P < 0.05), both is-
lands with high densities of oystercatchers (respectively 60
and 63 birds per km of shore). Inaccessible limpets were
not significantly different from accessible limpets at Cape
Columbine (t = 1.07, P > 0.1), an area with lower oys-
tercatcher density (two birds per km), although the trend
was in the same direction. Overall, inaccessible limpets
had a significantly lower SUI than accessible limpets (t =
2.93, P < 0.01).
(c) Limpets taken by oystercatchers had a significantly
lower SUI than accessible limpets at Malgas Island (t =
4.64, P < 0.001), but at Jutten Island the difference was
not significant (t = 0.25, P > 0.1) although the trend was
P. A. R. Hockey & G. M. Branch, 1983
in the same direction. Densities of oystercatchers at the
two sites are similarly high, but at Malgas Island, the
proportion of P. granularis in the diet (36%) is greater
than at Jutten Island (26%) (Hockey & Underhill, MS).
Overall, limpets taken by oystercatchers had a lower SUI
than all accessible limpets (t = 3.49, P < 0.001).
(d) Inaccessible limpets in depredated populations over-
all had a greater SUI than limpets in predator-free pop-
ulations (t = 2.32, P < 0.05).
Patella granularis grows allometrically, shell height in-
creasing faster than shell length (BRANCH, 1975), but SUI
was not correlated with limpet size (Table 1), in predator-
free populations (r = 0.17, P > 0.1), in all samples com-
bined (r = 0.45, P > 0.05) or in the additional samples
from Froggy Pond (r= 0.12, P > 0.2), so that variation
in limpet size can be eliminated as a factor influencing
SUIs. Similarly, wave action does not influence SUI. In
both samples from Froggy Pond (one sheltered, one ex-
posed) the mean SUI was 0.94 + 0.03.
DISCUSSION
The hypothesis that limpets in predator-free populations
will be more pear-shaped than those in depredated pop-
ulations was upheld. Similarly, the hypothesis that acces-
sible limpets will be more elliptical than inaccessible lim-
pets was supported in areas where the density of
oystercatchers is high. At a low density site, Cape Col-
umbine, the trend was the same but not significant.
The mean SUlIs for inaccessible limpets and limpets
consumed by oystercatchers were the same, but the former
was significantly higher (7.e., shells more elliptical) than
the mean SUI for predator-free populations. This further
supports the second hypothesis and implies that shell shape
is, at least to some extent, genetically determined, and that
predation by oystercatchers influences the limpet gene pool.
If this were not the case, inaccessible and predator-free
populations would have similar SUIs.
The possibility of a latitudinal influence on shell shape
was considered, but Table 1 clearly illustrates that there
is no trend in shape with decreasing latitude.
There are no other important vertebrate predators of
P. granularis. Very small individuals are occasionally tak-
en from mussel beds by Turnstones, Arenaria interpres,
and Whitefronted Plovers, Charadrius marginatus; and the
Giant Clingfish, Chorisochismus dentex, preys on limpets;
Page 141
but P. granularis is a negligible component of the diets of
these three species (STOBBS, 1980; BRANCH, 1981; person-
al observations).
From this we conclude that the selective influence by
oystercatchers alone on the genotypes of P. granularis is
sufficient to be detectable in the phenotypes.
ACKNOWLEDGMENTS
We thank John Cooper and Peter Ryan for collecting
specimens in northern Namibia and the Sea Fisheries Re-
search Institute for allowing access, and providing trans-
port, to islands under their control. Financial support was
provided by the South African National Committee for
Oceanographic Research (SANCOR). Statistical assis-
tance was provided by T. M. Crowe; R. Prys-Jones and
A. R. Palmer provided valuable comment on earlier drafts
of the manuscript.
LITERATURE CITED
BrancH, G.M. 1975. Ecology of Patella species from the Cape
Peninsula, South Africa. IV. Desiccation. Mar. Biol. 32:
179-188.
BRANCH, G. M. 1981. The biology of limpets: physical factors,
energy flow and ecological interactions. Oceanogr. Mar. Biol.
Ann. Rev. 19:235-380.
EBLING, F. J., J. A. Kircuinc, L. Muntz & C. M. Tay or.
1964. The ecology of Lough Ine XIII. Experimental ob-
servations on the destruction of Mytilus edulis and Nucella
lapillus by crabs. J. Anim. Ecol. 33:73-83.
FRANK, P. W. 1982. Effects of winter feeding on limpets by
Black Oystercatchers Haematopus bachmani. Ecology 63:
1352-1362.
Hartwick, E. B. 1981. Size gradients and shell polymorphism
of limpets with consideration of the role of predation. Ve-
liger 23:254-264.
Hockey, P. A. R. 1981. Feeding techniques of the African
Black Oystercatcher Haematopus moquim. In: J. Cooper (ed.),
Proc. Symp. Birds of the Sea and Shore, Cape Town, 1979
(Cape Town: African Seabird Group). pp. 99-115.
PALMER, A. R. 1979. Fish predation and the evolution of gas-
tropod shell sculpture: experimental and geographic evi-
dence. Evolution 33:697-713.
Stosss, R. E. 1980. Feeding habits of the Giant Clingfish
Chorisochismus dentex. S. Afr. J. Zool. 15:146-149.
VERMEIL, G. J. 1978. Biogeography and adaptation: patterns
of marine life. Harvard University Press, Cambridge. 332
PP-
The Veliger 26(2):142 (October 3, 1983)
THE VELIGER
© CMS, Inc., 1983
NOTES, INFORMATION & NEWS
A Range Extension of Nassarius miser (Dall, 1908)
by
Robert T. Howley
11760 Gilmore Street,
North Hollywood, California 91606
On October 2, 1982, an otter trawl was brought up from
a black mud bottom at a depth of 250 fathoms off Resort
Point, Palos Verdes Peninsula, Los Angeles County, Cal-
ifornia. Contents included the gastropods Acteocina eximia
(Baird, 1863), Amphissa bicolor (Dall, 1892), Bittiwm sp.,
Mitrella permodesta (Dall, 1890), Nassarius insculptus
(Carpenter, 1864) and a species of Nassarius represented
by five specimens. Those five shells were identified by Dr.
James McLean, Los Angeles County Museum of Natural
History, as Nassarius miser (Dall, 1908). One is deposited
at this museum and the others remain in the author’s
collection.
The northern range of Nassarius miser is cited as Cedros
Island, Baja California, Mexico, in A. M. KEEN (1971,
Sea Shells of Tropical West America, Stanford University
Press). The most northern part of Cedros Island is ap-
proximately 28°22’N latitude, 115°11’W longitude. Re-
sort Point is approximately 33°50'N latitude, 118°25’W
longitude. This is a range extension north of over 500 km
and, I believe, is the first published record of N. miser
from California.
I thank Ed Tarvyd, professor at Santa Monica City
College, through whose courtesy I was on board the re-
search vessel Vantuna. I also thank Dr. McLean, as well
as the captain and crew of the Vantuna.
California Malacozoological Society, Inc.
is a non-profit educational corporation (Articles of Incor-
poration No. 463389 were filed January 6, 1964 in the
office of the Secretary of State). The Society publishes a
scientific quarterly, The Veliger. Donations to the So-
ciety are used to pay a part of the production costs and
thus to keep the subscription rate at a minimum. Donors
may designate the Fund to which their contribution is to
be credited: Operating Fund (available for current pro-
duction); Savings Fund (available only for specified pur-
poses, such as publication of especially long and signifi-
cant papers); Endowment Fund (the income from which
is available. The principal is irrevocably dedicated to sci-
entific and educational purposes). Unassigned donations
will be used according to greatest need.
Contributions to the C.M.S., Inc. are deductible by do-
nors as provided in section 170 of the Internal Revenue
Code (for Federal income tax purposes). Bequests, lega-
cies, gifts, and devises are deductible for Federal estate
and gift tax purposes under section 2055, 2106, and 2522
of the Code. The Treasurer of the C.M.S., Inc. will issue
suitable receipts which may be used by Donors to sub-
stantiate their tax deductions.
Donations in Memory of Lucinda Draper
Mrs. Lucinda V. Draper, a native of lowa, passed away
suddenly on June 26. She was the wife of Bertram C.
Draper, and both have been long-time members of the
Conchological Club of California. A Memorial Fund has
been set up honoring Mrs. Draper, and in accordance
with the wishes of Mr. Draper, the proceeds have been
sent to the Veliger Endowment Fund. Donors include the
following: Mrs. Edith Abbott, Mrs. Jean Cate, the Con-
chological Club of Southern California, Mrs. Helen
DuShane, Mr. Joseph DuShane, Dr. James McLean and
Ms. Jo-Carol Ramsaran.
The California Malacozoological Society acknowledges
these generous donations with gratitude, and extends its
sympathy to Mr. Draper.
The Veliger 26(2):143-144 (October 3, 1983)
THE VELIGER
© CMS, Inc., 1983
BOOKS, PERIODICALS & PAMPHLETS
Marine Animals of Baja California
A Guide to the Common Fish
and Invertebrates
by DanieEL W. GOTSHALL. 1982. Sea Challengers: Los
Osos, California. 112 pp.; 213 color photographs. $17.95
paperback; $29.95 hard cover.
This field guide, designed to be used primarily by sport
divers and naturalists, provides photographs and brief
commentaries on 125 species of fishes and 62 species of
invertebrates encountered in the shallow waters surround-
ing the Baja California peninsula. For each photograph,
common and scientific names are listed along with habitat,
geographic range, maximum known size, and one or two
identifying characters.
The book’s primary flaws, many small sins of omission
in species coverage and identification, are mostly inten-
tional or at least understandable. Excluded are most of
the fishes and invertebrates whose southern range extends
down the outer coast of Baja from California (these are
covered in other books by the author). Also excluded are
small, difficult-to-identify animals and those to be found
only by digging or turning over rocks. Our readers par-
ticularly may regret the decision to include few mollusks
(the rationale is that mollusks are well covered in other
books)—only nine species of mollusks are illustrated com-
pared, for example, with 20 species of cnidarians. Also
worth noting is the fact that 14 of the 62 species of inver-
tebrates included are identified no further than to genus,
a result of limited taxonomic study in the area and the
author’s understandable reluctance to “guess” at identi-
fications from photographs.
Despite these limitations, this book is a useful and thor-
oughly enjoyable contribution. It is apparently the first
all-color photographic guide to both the fishes and inver-
tebrates of Baja California. The photographs are excep-
tionally fine, vivid and informative, and they are printed
with obvious care and craftsmanship. Both the author and
the publisher are to be complimented for the superb qual-
ity of the plates. In short, this book clearly belongs in the
luggage of anyone planning to visit the marine animals of
Baja California, just as it belongs on the shelves of arm-
chair naturalists who enjoy simply gazing at the beauty
of marine life.
D. W. Phillips
Tertiary Marine Pelecypods of California and
Baja California: Nuculidae Through Malleidae
by ELLEN JAMES Moore. 1983. U.S. Geological Survey
Professional Paper 1228-A, 108 pp., 27 pls., 2 figs., 8
tables.
In this, the first chapter of a projected compilation of
all Californian Tertiary marine mollusks, 233 species of
the Nuculidae, Malletiidae, Nuculanidae, Solemyidae,
Arcidae, Parallelodontidae, Cucullaeidae, Noetiidae, Li-
mopsidae, Glycymerididae, Manzanellidae, Mytilidae,
Pinnidae, Pteriidae, Isognomonidae, Pulvinitidae, and
Malleidae are illustrated, their original descriptions quot-
ed, comparisons made to other species, geographic and
stratigraphic range cited, depth range and habitat de-
scribed when known or inferred with confidence, and
modern taxonomic assignments made. The result is a su-
premely useful synthesis, sure to realize its goal of im-
proving the utility of marine mollusks in Cenozoic bio-
stratigraphy of the northeastern Pacific.
The work will also be a significant reference for Alas-
kan, northwestern Pacific, and Neotropical faunas, all of
which share genera and species with the Californian realm.
Of 52 genera of the included families that now occur in
the eastern Pacific region (Bering Strait to Cape Horn;
BERNARD, 1983, Canadian Spec. Publ. Fisheries & Aquat.
Sci. 61), 32 (62%) have a Tertiary fossil record in Cali-
fornia or Baja California. Neontologists ignore this at their
peril.
Type localities, location of type material, and synony-
mies are given; where possible, the illustrations are of type
specimens. For large families, distribution tables show
graphically the geographic and geologic distribution of
eastern Pacific species from Alaska to Central and/or South
America. Occurrence in the Californias is listed by for-
mation; a table gives series-epoch assignments for all for-
mations cited.
Even a compilatory work like this one contains some
subjective judgments—particularly on taxonomic mat-
ters—hence, room for debate. For example, it will be in-
teresting to see whether Adula? mcknight: (Hanna, 1927)
ultimately proves to be an Adula or perhaps, with its coiled,
nearly terminal beaks, a species of Botula. I doubt whether
Perna montana Conrad, 1857, is properly assigned to the
mytilid genus Perna Retzius, 1788, rather than the isogno-
monid Perna Bruguiére, 1789, which Conrad seems to
have had in mind.
All debater’s points aside, the “Moore Synthesis” will
be a paleontologists’ companion and standard volume for
years to come. I hope that the Geological Survey will give
high priority to the production and publication of future
chapters.
B. Roth
Page 144
Morphologie und Bildung der fruhontogenetischen
Gehause bei conchiferen Mollusken
(Morphology and formation of the early ontogenetic
shells of conchiferan mollusks)
by KLAus BANDEL. 1982. Facies 7:1-198, pls. 1-22, 109
text figs., 6 tables, Erlangen. (In German with English
summaries in the text.)
This is a must for every student not only of early on-
togenetic shells, but of the entire molluscan ontogeny and
phylogeny. The work starts with detailed personal obser-
vations on selected species of archeogastropods sensu stric-
to, neritaceans, mesogastropods, neogastropods, ammo-
nites, and recent cephalopods (Sepia, Spirula, Nautilus),
to lead the reader into a discussion on successively more
comprehensive aspects of the ontogeny, phylogeny, and
classification of the phylum Mollusca.
Highlights are:
—1in archeogastropod ontogeny, the presentation of a course
of events different from most textbooks, which, if con-
firmed and generalized, must mean that the Garstang-
Crofts model of archeogastropod torsion is now out;
—a rejection of the idea that Fissurellidae gave rise to
Scissurellidae by means of neoteny;
—discovery of shell pores in Puncturella and Emarginula,
but not in Fissurella;
—further evidence that Neritacea show little similarity to
the rest of the archeogastropods, but are related to the
mesogastropods;
—examples of variations in ontogeny of higher gastro-
pods, which suggest that ecological and functional pres-
sures frequently changed the course of gastropod ontog-
mys
—precisions and corrections to previous studies on the
earliest ontogeny of ammonite shells and comparison
with shells of living cephalopods; a modification of the
model of monoplacophoran or early gastropod origin of
cephalopods; |
The Veliger, Vol. 26, No. 2
—a discussion of the characters of monoplacophorans; the
question of primary versus secondary metamery cannot
be solved with the present knowledge of this class, a
circumstance aggravated by the shortcomings of the fos-
sil record: beyond the insufficient state of preservation,
there is the ambiguity of properties such as the position
of the apex, the bilateral symmetry of the shell, and
apparently metameric muscle impressions, which may
be found in similar appearance in limpet-like gastro-
pods as well; in many fossils not even the distinction
between monoplacophorans and gastropods is proven.
—many critical comments on the taxonomic significance
of various properties are interspersed in the text: for
example, of archeogastropod primary shell sculpture; of
the slit and its derivatives; of characters of limpet-like
shells such as secondary mineral deposits (callus) in the
apex, loss of the primary shell (the “protoconch’’), and
development of secondary bilateral symmetry; of the
shape and size of the inner protoconch of cephalopods;
and of the presence of shell pores.
To the taxonomist one impression remains: many fea-
tures, from the muscle-scars of limpet-like shells, to the
cephalopodan inner protoconch, and to the bilateral sym-
metry, seem to be determined by function and physiology,
and, thus, might have been developed repeatedly, rather
than indicating the common origin of their bearers. Some
soul-searching needs to commence, especially among those
concerned with paleozoic mollusks and with the classifi-
cation of the larger taxonomic units.
The author has combined a plethora of observations of
his own with vigorous literature digestion. Having himself
brought down a few theories might have cautioned him
not to create too many new ones, except for his model of
archeogastropod torsion. Regardless, this work provides
in every chapter food for thought and stimuli for further
research. By reading this book, one can relive the fasci-
nation exerted by the observation of growth, construction,
and final form that carried the author through his studies.
D. Kadolsky
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The sequence of manuscript components should be as follows in most cases: title page,
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Literature cited
References in the text should be given by the name of the author(s) followed by the
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from the text. Each citation must be complete and in the following form:
a) Periodicals
CATE, J. M. 1962. On the identification of five Pacific Mitra. The Veliger 4:132-
134.
b) Books
YONGE, C. M. & T. E. THOMPSON. 1976. Living marine molluscs. Collins,
London. 288 pp.
c) Composite works
FEDER, H. M. 1980. Asteroidea: the sea stars. Jn: R. H. Morris, D. P. Abbott & E.
C. Haderlie (eds.), Intertidal invertebrates of California. Stanford Univ. Press, Stan-
ford, Calif. pp. 117-135.
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CONTENTS — Continued
_Barnacle attachment on live Nautilus: implications for Nautilus growth rate.
NeEIU H.. LANDMAN 532055,5, Geis ek oe eye etic ee atts een ens ara 124
Distribution and abundance of Caecum cornucopiae (Gastropoda: Prosobranchia)
on Cladophora crystallina mats in a Bahamian salt water lake.
BETSY DAY 55s coer ete a Ree cae ore ONCE Rea at ae a 128
The Bermudan and Caribbean sacoglossan mollusk Elysia flava Verrill now
recorded from the Greek Aegean Sea.
T., B.. THOMPSON 2 5. oo pelea ge tear ares cP ees) Oe eae oe a 136
Do oystercatchers influence limpet shell shape?
PA: R. HOCKEY AND Gai MEIBRANCED Selim ey Annee ee 139
NOTES, INFORMATION & NEWS
A range extension of Nassarius miser (Dall, 1908).
ROBERT "THROW Y ss ete tein ON a 142
UJ
ISSN 0042-3211
THE
VELIGER
A Quarterly published by
CALIFORNIA MALACOZOOLOGICAL SOCIETY, INC.
Berkeley, California
R. Stohler, Founding Editor
Volume 26 January 3, 1984 Number 3
CONTENTS
Activity, dispersion, and size of Lanistes nyassanus and L. solidus (Gastropoda,
Ampullariidae) over the depth gradient at Cape Maclear, Lake Malawi,
Africa.
S. M. Loupa, K. R. McKaye, T. D. KocHer, AND C. J. STACKHOUSE ... 145
The Recent Crassatellinae of the eastern Pacific, with some notes on Crassinella.
EUGENE COAN i153)
Description of five new species of Hawaiian Eulimidae.
ANDERS WAREN, BEATRICE L. BURCH, AND THOMas A. BURCH ......... 170
A new species of Ischnochiton (Mollusca: Polyplacophora) in the Gulf of Cali-
fornia.
LANG ONL OM PAE RIRE IRAs Metin ne sy mre et ce Golly) ate Nye eoeaull 2a ei Wie Wi 7)
Records of Cuthona pustulata (Alder & Hancock, 1854) from the Canadian
Pacific.
MERRENCE Mc \GOSEINER AND SANDRA V. MILLEN ......0.............. 183
The ecology of Parvilucina tenuisculpta (Carpenter, 1864) (Bivalvia: Lucinidae)
on the southern California borderland.
GIEBERGAE WONES ANDEBRUGE) bMlHOMPSON ses eia le ae 188
Hybridization of two populations of a marine opisthobranch with different de-
velopmental patterns.
HItiary H. WEST, JUNE F. HARRIGAN, AND SIDNEY K. PIERCE......... ea
Ve Sit TESCN Ag,
CONTENTS — Continued /
AM 2 7 qua
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THE VELIGER
Scope of the journal
The Veliger is open to original papers pertaining to any problem concerned with mol-
lusks.
This is meant to make facilities available for publication of original articles from a
wide field of endeavor. Papers dealing with anatomical, cytological, distributional, eco-
logical, histological, morphological, physiological, taxonomic, etc., aspects of marine,
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Editorial Board
Donald P. Abbott, Emeritus, Hopkins Marine Station of Stanford University
Hans Bertsch, Universidad Autonoma de Baja California
James T. Carlton, Williams College—Mystic Seaport
J. Wyatt Durham, University of California, Berkeley
Cadet Hand, University of California, Berkeley
Carole S. Hickman, University of California, Berkeley
A. Myra Keen, Emerita, Stanford University
Frank A. Pitelka, University of California, Berkeley
Peter U. Rodda, California Academy of Sciences, San Francisco
Clyde F. E. Roper, National Museum of Natural History, Washington
Judith Terry Smith, Stanford University
Ralph I. Smith, University of California, Berkeley
Wayne P. Sousa, University of California, Berkeley
T. E. Thompson, University of Bristol, England
Alex Tompa, University of Michigan, Ann Arbor
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The Veliger 26(3):145-152 (January 3, 1984)
THE VELIGER
© CMS, Inc., 1984
Activity, Dispersion, and Size of Lanistes nyassanus
and L. solidus (Gastropoda, Ampullariidae) over the
Depth Gradient at Cape Maclear, Lake Malawi, Africa
by
S. M. LOUDA,'* K. R. McKAYE,' T. D. KOCHER,?
AND C. J. STACKHOUSE?
' Duke University Marine Laboratory, Beaufort, North Carolina 28516
? Department of Environmental, Population and Organismic Biology,
University of Colorado, Boulder, Colorado 80309
> Route 3, Box 274, Hillsborough, North Carolina 27278
Abstract.
We examined the hypothesis that a diel cycle of activity accounts for daily variation in
observed density of two endemic, lacustrine species of Lanistes: L. nyassanus and L. solidus. Snail activity,
density, and size were recorded over the 1.5-35.5 m portion of the water depth gradient at Cape
Maclear, Malawi, in the southern part of Lake Malawi, during both cool-wet (1980, 1981) and warm-
dry seasons (1981, 1982). Population parameters were quantified. A diel cycle of activity occurred for
both species of Lanistes at all depths in both seasons. The population activity patterns and dynamics of
these related species are hypothesized to: (1) be independent of each other but correlated with micro-
habitat structure; and (2) reflect food availability in one case (L. solidus) as well as a refuge from cichlid
predation for recruits of both species.
INTRODUCTION
THE ENDEMIC prosobranch mollusks of Lake Malawi,
Africa, form a complex, relatively speciose group; as such
they represent a model of the more extensive gastropod
radiation observed in tropical deep lakes compared to tem-
perate ones (Boss, 1978; HUTCHINSON, in press). Yet, few
data exist on the activity, dynamics, or interactions of any
of these assemblages (LIVINGSTONE, 1981, p. 179). Two
particular aspects formed the focus of our study of the
population dynamics of the apple snails (Ampullariidae)
at Cape Maclear, Lake Malawi: activity patterns and
population distribution patterns along the environmental
depth gradient.
Activity patterns are characteristic for species and sig-
nificant for the dynamics and interactions of populations
in communities (ORIANS & SOLBRIG, 1977). Cycles in ac-
tivity can influence apparent density (LouDA & McKayeE,
1982), resource utilization (ORIANS & SOLBRIG, 1977),
and vulnerability to predation (PHILLIPS, 1977; WELLS,
1980). Furthermore, predation by fishes has been hypoth-
esized to be a significant selective pressure on aquatic gas-
* Current mailing address: School of Life Sciences, University
of Nebraska, Lincoln, Nebraska 68588.
tropods in general (PHILLIPS, 1977; VERMEIJ & COvIcH,
1978; WELLS, 1980) and on two Lake Malawi species in
particular (WRIGHT et al., 1967; LouDA & McKaye,
1982). Offset diel patterns of activity seem to be an im-
portant aspect of the fish-snail interaction in Lake Ma-
lawi. The molluscivorous cichlid fishes are diurnal
(McKaye, unpublished data; Louda, personal observa-
tion) whereas the gastropods are nocturnal (LOUDA &
McKayeE, 1982; Louda, unpublished data). A diel pattern
of movement, along with partial burrowing, which has
been documented for marked snails in shallow (1-3 m)
water (LOUDA & McKayeE, 1982), accounts for anecdotal
observations of variation in density (GRAY, 1980) of Lan-
istes nyassanus Dohrn, 1865, over a daily cycle.
In the work described here we examine the consistency
of the diel activity pattern of L. nyassanus: (1) at a range
of depths (1-34 m), (2) in different seasons (cool-dry ver-
sus warm-wet), and (3) in relation to that of a co-occur-
ring species (L. solidus Smith, 1877). Additionally, we
quantify population density, dispersion, and size distri-
butions along the depth contour for both species.
Three major questions are asked. First, does a diel ac-
tivity pattern occur for both species of Lanzstes and is the
pattern consistent among depths? Second, what are the
population parameters with depth and is there any evi-
Page 146
dence of competitive interaction between congeners, species
that would be predicted to have similar ecological require-
ments? Third, is snail distribution related to predation
and microhabitat?
STUDY SYSTEM
Our observations were made along a 4-km section of sandy
beach adjacent to the Fisheries Research Station at Cape
Maclear (34°50’E; 14°5’S), in the southern region of Lake
Malawi, 12 km west of Monkey Bay, Malawi (see LouDA
& McKaye, 1982, fig. 1). This section of beach has high
densities of both Lanistes nyassanus and L. solidus in shal-
low water (Gray, 1980; LouDA & McKayeE, 1982); they
coexist there with about 16 species of smaller gastropods
(LouDaA et al., 1983). There is an annual cycle in water
temperature; it is highest (29°C) in the warm, wet season
of January-April and lowest (21°C) in the cool, dry sea-
son of June-August (McKayeE, 1983).
The Ampullariidae (=Pilidae) are medium to large (to-
tal length = 10 cm), globose snails characterized by a tae-
nioglossate radula and a concentric operculum (WORLD
HEALTH ORGANIZATION, 1977; BROWN, 1980). The two
species of Lanistes are endemic to Lake Malawi and co-
exist in the shallow portion of the shore around Cape
Maclear. Lanistes nyassanus is distinctive, being more de-
pressed (BROWN, 1980, fig. 28) and usually larger and
heavier than other species of Lanistes. However, L. solidus
is similar to L. ellipticus Martens, 1866, which occurs
primarily on marsh vegetation around the lake (CROWLEY
et al., 1964; CANTRELL, 1979). In fact, L. solidus may be
a heavier lacustrine form of L. ellipticus (BROWN, 1980,
and personal communication).
METHODS
Our observations of Lanistes species were made using
SCUBA during four periods: 18 June—30 August 1980,
17 February—20 March 1981, 7 August-1 September
1981, and 9-23 February 1982. June-August is the cool,
dry season; February-March is in the warm, rainy season
at this latitude.
The following data were collected by divers visually
searching 12.5 X 2-m transects placed along specified depth
contours: (1) number of L. nyassanus and L. solidus, (2)
activity, and (3) aperture length of all Lanistes encoun-
tered. The high (96%) efficiency of visual search using
SCUBA over the open sand habitat was verified by (a)
direct search (hand raking) of the top 5 cm of substrate
(N = 100 m?), (b) quadrat collection (LOUDA et al.,
1983), and (c) the consistency of visual density observa-
tions in the morning and afternoon on a permanent 128
m? grid (LouDA & McKaye, 1982; Loupa, unpublished
data). Inter-observer agreement also was verified (Krus-
kal-Wallis Test, P > 0.10). All data were collected at 12
3.0-m depth intervals from 1.5-35.5 m.
Snail activity was scored as (1) more than one-half bur-
The Veliger, Vol. 26, No. 3
ied in the substrate or (2) less than one-half buried or
active on the substrate surface. During the first two ob-
servation periods we also recorded whether or not active
snails were in a semi-inverted posture with foot extended
into the current. This behavior, presumably feeding (de-
scribed in LouDA & McKayE, 1982), is of special interest.
Although filter feeding is known among ampullariids
(JOHNSON, 1952; CHEESMAN, 1956; McC ary, 1964), it
is relatively uncommon among gastropods and is not the
usual, rasping mode of feeding of most Ampullariidae
(YONGE, 1938).
Aperture length was used as an estimate of size because
it represents body size, varies less than other measures as
shell wear occurs (FOTHERINGHAM, 1971; Loupba, 1979),
and correlates well with total shell length for L. nyassanus
(Loupa & McKayeE, 1982).
RESULTS
Activity
Afternoon activity always exceeded morning activity for
both species. A significantly higher proportion of individ-
uals were active on the substrate surface between 1500
and 1800 h than between 0500 and 0800 h at all depths
(Figure 1) in both seasons (Table 1). Occurrence of the
inverted posture among all snails observed did not vary
with time of day; however, occurrence was higher in the
cool season than in the warm season for both species (Ta-
ble 2). Among active snails of both species, the proportion
in the inverted posture, and presumed to be feeding (LOUDA
& McKayéE, 1982), was significantly greater in the morn-
ing than in the afterncon; also, among the active L. solidus
there was a significant decrease in this type of activity
during the warm season compared to that in the cool sea-
son (Table 2).
Density
Four main points stand out in the data. First, the den-
sity of both species was greatest in shallow water. The
highest densities of Lanistes nyassanus (18.3/25 m?) were
observed at a depth of 1.5 m (Table 3A) and those of L.
solidus (72.0/25 m?) at a depth of 4.6 m (Table 3B). Den-
sity of L. nyassanus over the rest of the gradient below
10.8 m remained relatively constant (4—8/25 m?). Density
of L. solidus, however, dropped sharply to less than 1/25
m? below 4.6 m (Table 3B). No live specimens of L. solidus
have been observed by us below 22 m in the Cape Maclear
region of southern Lake Malawi.
Second, until 1982 the densities of L. solidus were gen-
erally much higher than those of L. nyassanus in the shal-
low area in which they overlap. The density of L. solidus
at 4.6 m was four to eight times higher than the density
of L. nyassanus for all paired 1980 and 1981 observations.
The density of L. solidus at 1.5 m also was greater for the
last three out of the four dates (Table 3).
S. M. Louda et al., 1984
Active
Proportion
2 5 8 111417 20
Depth (m)
Figure 1
Average proportion active between 0500 and 0800 h (@---@)
and between 1500 and 1800 h (O—Q), both seasons combined,
along the depth gradient at Cape Maclear (X + 95% confidence
limits; statistics on arcsine-transformed data). A. Lanistes nyas-
sanus (N = 305, 183, 153, 183, 136 and 50 at depths to 32 m,
respectively). B. Lanistes solidus (N = 255, 394, 4, 2 and 1 at
depths to 17 m, respectively).
Third, the distribution of L. nyassanus tended to change
over the depth gradient between seasons. The highest den-
sity of L. nyassanus was deeper in each cool, dry season
than it was in the succeeding warm, wet season (Table
3A). During the 1980 cool season, density of L. nyassanus
was highest at 4.6 m. In the succeeding warm season of
February-March 1981, L. nyassanus density increased
significantly at 1.5 m and decreased at three greater, ad-
jacent depths (Table 3A). In the second cool, dry season
(1981) L. nyassanus numbers dropped sharply in the shal-
low depths (1.5-7.7 m) while increasing significantly at
10.8 m (Table 3A). Increases at one depth were accom-
panied by decreases at other depths for L. nyassanus; thus,
distribution, rather than absolute number, must have
changed between seasons. Finally, in the second warm,
wet season the highest densities were again at shallower
depths (4.6 and 1.5 m); however, all densities were lower,
Page 147
Table 1
Activity of Lanistes species by season (cool, dry = June-
August 1980 and 1981; warm, wet = February-March
1981 and 1982).
Species Morning Afternoon
Season (0500- (1500-
Parameter 0800 h) 1800 h) Total
L. nyassanus
Cool, dry
N 864 890 1754
Proportion active 0.434 0.804 0.622
95% CI. 0.39-0.47 0.76-0.84 0.59-0.64
Warm, wet
N 524 540 1064
Proportion active 0.391 0.592 0.493
95% CI. 0.34-0.43 0.55-0.62 0.46-0.52
L. solidus
Cool, dry
N 540 660 1200
Proportion active 0.293 0.686 0.509
95% CI. 0.24-0.34 0.64-0.73 0.49-0.53
Warm, wet
N 438 412 850
Proportion active 0.311 0.568 0.435
95% C.1. 0.27-0.33 0.52-0.62 0.38-0.47
suggesting a decline in absolute numbers as well as a shift
in distribution.
Fourth, the density of L. solidus dropped over the 20
month period (Table 3B). Density of L. solidus remained
highest at the 4.6-m depth in all seasons, but total num-
bers dropped markedly in each subsequent season after
the first year (Table 3B). This decrease in L. solidus den-
sity at 4.6 m was not accompanied by increases in density
at other depths except in the warm wet season of 1981
(Table 3B); thus, emigration or mortality occurred for L.
solidus over the year between the warm wet season of 1981
and that of 1982.
Size Distribution
The average size of individuals generally increased as
depth increased. Initially for L. nyassanus, average aper-
ture length was lowest (3.0 cm) at 4.6 m and increased
(to 3.6 cm) at 29.4-m depth (Table 4A). The trend of
increased size of L. nyassanus with increased depth was
consistent for all seasons. The exception was the equal,
or greater, average size at the shallowest depth (1.5 m)
compared to those at the next, adjacent (4.6 m) depth in
all four samples (Table 4A). Interestingly, individuals of
L. nyassanus were significantly larger in the warm seasons
than in the cool seasons (Table 4A). Lanistes solidus av-
eraged 2.4 cm (SE 0.03); but, in contrast, these snails were
consistently smaller in the warm wet season than in the
cool, dry (Table 4B). Size was generally lower in 1981 at
Page 148
The Veliger, Vol. 26, No. 3
Table 2
Occurrence of inverted posture for species of Lanistes at Cape Maclear by season (cool, dry season 1980; warm, wet
season 1981) and by time of day (AM = 0500-0800 h; PM = 1500-1800 h). * = P = 0.05; ** = P < 0.01.
Total Number Number
Species observed active inverted
L. nyassanus
Time
AM 739 315 50
PM 726 535 52
Season
Warm, wet 505 266 26
Cool, dry 960 584 76
L. solidus
Time
AM 551 197 24
PM 675 447 19
Season
Warm, wet 592 238 8
Cool, dry 634 406 36
4.6 m, 2.e., where over 95% of the individuals occurred
(Table 3B). Furthermore, the few individuals found at
deeper depths, below 4.6 m, were large (N = 22, = D7
cm, SE = 0.09) for the population (Table 4B), in a pat-
tern similar to that of L. nyassanus.
Three main facts are evident from the size-frequency
data. First, no significant differences related to season were
observed in size-frequency distributions for either species
(Figure 2). Second, the modal (3.3-3.4 cm) and mean
(3.2-3.5 cm) sizes for L. nyassanus for each season were
higher than those for L. solidus (mode = 2.3 cm, mean =
2.3-2.4 cm) (Figure 2). Third, no small, young specimens
of either species, those with an aperture less than 1.0 cm,
were observed on the transects in either warm or cool
seasons. Because small individuals (<1.0 cm total length)
are extremely rare but after extensive searching have been
found among the vascular macrophyte stems at 3-5 m in
the study region (LouDA & McKayeE, 1982), the data here
support the suggestion that the occurrence and recruit-
ment of small individuals of Lanistes is patchy, extremely
restricted, and related to microhabitat heterogeneity.
DISCUSSION
Casual observations suggested lower densities of Lanistes
species in the mornings than in the afternoons at Cape
Maclear (GRAY, 1980). However, by following marked
snails in shallow water, LouDA & McKaye (1982) found
that actual, visually-recorded quantitative densities did not
change; instead, partial burial of L. nyassanus via diel
movement into and out of the sand substrate occurred,
giving the superficial impression of changing density. The
present study extends the available observations over the
environmental gradient. We found that a diel pattern of
Inverted among total Inverted among active
7o Gi 7 1
6.8 15.9 ae
79 0.09 97 WoMil
oil oy 9.8
79 395) 13.0 1.80
4.4 WAZ **
28 2.14 43 13.78
1.4 ee 3.4 =
55 14.45 8.6 6.67
activity occurred for both species, at all depths, and in
both seasons (Figure 1, Table 1).
The three main hypotheses to explain the adaptive val-
ue of a diel pattern are: (1) physiological limits to activity,
(2) intrinsic (canalized) gastropod behavior, and (3) pred-
ator avoidance. Further work is required to separate these
hypotheses. Our observations, however, suggest physio-
logical limits to diel activity are unlikely. Although overall
activity appeared lower during the warm season (Table
1), it was high under all conditions.
Predation pressure was intense, reinforcing any intrin-
sic tendency toward nocturnal activity. The predators on
gastropods, such as birds (e.g., ZACH, 1978), crabs (VER-
MEIJ & CovicH, 1978), or fishes (FRYER & ILES, 1972;
MckKayeE, personal observation), are diurnal, visual hunt-
ers. Effective diurnal predators should exert strong selec-
tive pressure for nocturnal activity on their prey. Both
shore birds and cichlids were common at Cape Maclear.
Further, shore birds foraged frequently in the shallow
water between O and 0.5 m depth. Also, densities of the
molluscivorous cichlid fishes (Cyrtocara [Haplochromis]
anaphyrmis, C. mola, C. placodon, C. sphaerodon, and Tre-
matocranus microstoma: see FRYER & ILES, 1972) were
high between 1 and 15-m water depth in our study area
(McKaye, unpublished data). Cichlids were observed at-
tempting to feed on an extended foot or siphon of the
larger Lanistes individuals; these attacks on large snails
were generally unsuccessful (McKaye and Louda, per-
sonal observation). Additionally, stomach-content analysis
showed small snails were particularly vulnerable to cich-
lid predators (McKaye and Louda, unpublished data).
Temporal as well as spatial avoidance of the fish preda-
tion appeared important in recruitment and survival. Small
individuals of both species were notably thin-shelled
S. M. Louda e¢ al., 1984
Page 149
Table 3
Apple snail density (number/25 m?) over the depth contour at Cape Maclear in southern Lake Malawi for each season
sampled; highest density in each season is underlined.
Species
Season 15 4.6 Voll 10.8
A. Lanistes nyassanus
Cool, dry 1980
x 8.9 15.8 6.6 7.8
SE 1.34 DES 0.73 1.14
N 8 4 14 14
Warm, wet 1981
x 18.3 V2), 3.9 1.9
SE DOA, 1.38 0.85 0.35
N 12 12 8 8
Cool, dry 1981
x 4.4 2.9 3.8 de
SE 0.98 1.59 0.81 1.12
N 16 16 16 16
Warm, wet 1982
Xx 557 _7.6 2.6 4.4
SE 0.86 0.59 0.76 0.75
N 16 16 16 16
B. Lanistes solidus
Cool, dry 1980
XK 4.6 72.0 0.2 0.2
SE 0.62 9.34 0.11 0.13
N 12 8 12 12
Warm, wet 1981
x 36.0 55.2 0.2 0.2
SE 12.75 19.61 0.61 0.25
N 10 12 8 8
Cool, dry 1981
Xx 13.6 24.3 0.2 0.2
SE 1.98 2.41 0.10 0.14
N 16 16 16 16
Warm, wet 1982
x 7.4 9.4 0.3 0.0
SE 0.72 1.00 0.12 0.00
N 16 16 16 16
(WoRLD HEALTH ORGANIZATION, 1977), extremely fra-
gile (Louda, personal observation) and rare (Figure 2).
Also, small, young snails were observed in systematic
searches only in protected microhabitats, such as empty
adult shells or among the vascular macrophyte stems. These
individuals are highly susceptible to the molluscivorous
cichlids present (LoUDA & McKayeE, 1982; McKaye and
Louda, unpublished data).
Our observations over the 20 months suggest that the
39)
0.42
0.00
0.0
0.00
16
0.0
0.00
16
Depth (m)
17.0 20.1 23.1 26.3 29.4 3,5) 35.6
UP 5.0 5.8 6.8 8.0
1.20 0.78 0.65 0.77 1.30
14 14 16 12 8 — —
2.6 4.4 8.2 5.9
0.42 0.73 1.59 0.98
8 8 12 8
4.3 5.5 BS VD 5.3 5.4 6.5
0.51 0.64 0.54 0.93 0.54 0.66 1.50
16 16 16 16 12 16 4
2.5 De? 2.9 1.4 2.1 1.6
0.34 0.55 0.55 0.30 0.42 0.26
16 16 16 16 16 16 =
0.1 0.1 0.0 0.0
0.08 0.08 0.00 0.00
12 12 12 12
0.0 0.0 0.0 0.0
0.00 0.00 0.00 0.00
8 8 8 8
0.1 0.0 0.0 0.0 0.0 0.0 0.0
0.06 0.00 0.00 0.00 0.00 0.00 0.00
16 16 16 16 16 16 16
0.0 0.0 0.0 0.0 0.0 0.0
0.00 0.00 0.00 0.00 0.00 0.00
16 16 16 16 16 16 ==
occurrence of both species was related to vascular macro-
phyte cover. Potamogeton trichocoides, the predominant
macrophyte in August 1980, decreased from 25% cover to
less than 1% cover between February and August, 1981
(Louda, unpublished data). At the same time the distri-
bution and density of both species changed. Total density
declined for both species by the warm, wet season of 1982
(Table 3), especially for L. solidus. The highest densities
of L. nyassanus declined and shifted deeper by August
Page 150
Table 4
The Veliger, Vol. 26, No. 3
Lanistes size distributions by season: aperture length at sampling depths along the bottom profile at Cape Maclear,
southern Lake Malawi, throughout the study, July 1980-March 1982; smallest and largest mean sizes along each seasonal
transect are underlined once and twice, respectively.
Total
over
Species all
Season depths
A. Lanistes nyassanus
Cool, dry 1980
Xx 3.3
SE 0.02
N 1038
Warm, wet 1981
x 3.5
SE 0.02
N 582
Cool, dry 1981
XK 3.4
SE 0.01
N 961
Warm, wet 1982
XK 3.5
SE 0.02
N 559
B. Lanistes solidus
Cool, dry 1980
Xx 2.4
SE 0.02
N 637
Warm, wet 1981
x 2.3
SE 0.01
N 472
Cool, dry 1981
XK 2.4
SE 0.04
N 564
Warm, wet 1982
xX 2.3
SE 0.02
N 272
1.5)
0.01
283
2.4
0.04
217
2.2
0.03
121
4.6
0.05
0.04
123
2.3
0.02
146
Voll
3
0.04
102
3.4
0.08
29
3.4
0.06
60
3.5
0.08
41
2.4
10.8
32
0.03
124
0.10
2.4
0.49
Depth (m)
13.9 17.0 20.1 2erl 26.3 29.4 32.5 35.6
Ball 3.2 3.3) 3.4 3.4 3.6
0.06 0.04 0.04 0.04 0.04 0.04
70 115 81 92 82 64 =
3.6 3.4 35) 3.6 3.6
0.12 0.08 0.06 0.03 05
21 31 35 102 39 = = =
32 3.3 3.4 3.4 3.5 3.6 3.6 3.8
0.02 0.04 0.05 0.08 0.03 0.04 0.03 .06
84 69 88 53 116 83 87 26
3.4 3.4 3.6 35) 3.6 Sell Bal
0.07 0.07 0.06 0.04 0.09 .04 .06
34 39 36 45 23 33 24 —
i 23 2.6 oe ae
0 1 1 0 0
3.0
1 0 0 0 0 — — —
DAS) — — — —
1 0 0 0) 0 0 0 0
0 0 0 0 0 0 0) —
S. M. Louda e al., 1984
— e — Cool-dry
--- © --Warm-wet
(%)
Frequency
1 2 3 4 5
Aperture Length (cm)
Figure 2
Frequency distribution of relative size (aperture length in cm)
for each species at Cape Maclear for each season sampled in
1981 (@ = cool-dry; = warm-wet). A. Lanistes nyassanus; B.
Lanistes solidus (all N’s > 500 per season).
1981 (Table 3A); those of L. solidus had halved but did
not shift. These changes were correlated with the decline
of macrophytes at 3-5 m depth (Pearson’s rank correla-
tion coefficient, P < 0.05).
Each species was associated with the macrophytes, but
in different ways, rather than associated with each other.
The observations suggest a refuge hypothesis for L. nyas-
sanus. Maximal L. nyassanus densities occurred initially
in and above the macrophyte bed at 3-5 m (Table 3A;
LoupA & McKayeE, 1982). The smallest individuals of
L. nyassanus occurred among the weeds, at 4.6 m during
the first two sampling periods but deeper, at 10.8-13.9
m, after the weeds declined (Table 4A). Maximal density
of L. nyassanus at any depth was lower after weed dis-
appearance than before (Table 3A).
Page 151
The refuge hypothesis for adults of L. solidus is less
likely. Average size did not vary between snails in and
outside the bed at 3-5 m (Table 4B). However, with the
disappearance of the weeds by the cool dry season 1981,
densities declined and became more equally divided be-
tween the two shallower depths (Table 3B). The weeds
may provide a refuge for recruitment of young L. solidus
since the only individuals less than 1.0 cm observed were
found among the weed stems. An alternative hypothesis
for the occurrence of adult L. solidus in the shallow water
is derived from feeding observations. Although both species
will feed on dead plant and animal matter, L. solidus scav-
enged significantly more frequently than L. nyassanus
(Louda, unpublished data). Indeed, L. solidus can be
“baited” with organic matter. The weed bed, besides pro-
viding a potential source of scavengable plant material,
also acted as a trap for free floating items carried by the
water current (Louda, personal observation). Thus, high
density of adult L. solidus in the bed would reflect in-
creased food availability.
In sum, we propose that the weed-bed microhabitat
allowed upward extension of high densities of L. nyassanus
by providing a refuge for smaller individuals and a poten-
tial recruitment site for young. Also, the weed bed led to
a high density of adult L. solidus by providing a concen-
trated source of a sporadic resource, scavengable matter.
With loss of the weed bed, dispersion and decline of both
Lanistes populations occurred.
ACKNOWLEDGMENTS
We thank all who contributed to this study. In particular,
W. N. Gray elicited our interest in the gastropods and
identified the Potamogeton. In addition, D. S. Brown, C.
T. Grace, I. Grace, G. E. Hutchinson, and P. N. Reinthal
discussed the project and encouraged us; P. N. Reinthal,
D. Reinthal and R. D. Zweig helped gather data; W. N.
Gray, D. S. C. Lewis, D. W. Phillips, P. N. Reinthal and
two anonymous reviewers suggested improvements in the
manuscript. The Malawi Government gave permission to
study the aquatic ecosystem at Cape Maclear and we are
most grateful. Support to K.R.M. was provided by NSF
grant DEB-79-12338.
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CHEESMAN, D. F. 1956. The snail’s foot as a Langmuir Trough.
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The Veliger 26(3):153-169 (January 3, 1984)
THE VELIGER
© CMS, Inc., 1984
‘The Recent Crassatellinae of the Eastern Pacific,
with Some Notes on Crassinella
by
EUGENE COAN
Department of Invertebrate Zoology, California Academy of Sciences,
Golden Gate Park, San Francisco, California 94118
Abstract. The three eastern Pacific species of the Crassatellinae belong in Eucrassatella Iredale,
1924. Hybolophus Stewart, 1930, is regarded as a synonym of this genus, as is the recently proposed
but unavailable Eucrassinella Cruz, 1980. The rare E. fluctuata (Carpenter, 1864) occurs off the Chan-
nel Islands of southern California at a mean depth of 88 m; a synonym is the Plio-Pleistocene Cras-
satellites lomitensis Oldroyd, 1924. Crassatella marginata Keep, 1887, ex Carpenter MS, which has been
synonymized with E. fluctuata, is instead based on specimens of the bernardinid genus Halodakra,
perhaps Halodakra salmonea (Carpenter, 1864). Eucrassatella gibbosa (Sowerby', 1832) occurs from the
Gulf of California to Peru at a mean depth of 32 m. Added to its synonymy are Eucrassatella (Hybol-
ophus) gibbosa tucilla Olsson, 1932, and Eucrassinella manabiensis and E. aequitorialis Cruz, 1980.
Crassatella corbuloides Reeve, 1842, which has been synonymized with E. gibbosa, is instead an Austra-
lian taxon. The Venezuelan Eucrassatella antillarum (Reeve, 1842) is synonymized with the eastern
Pacific E. digueti (Lamy, 1917). In the eastern Pacific this species occurs at a mean depth of 45 m from
the Gulf of California to Ecuador. Newly added to its synonymy is Crassatella laevis A. Adams, 1854,
from the Caribbean. Lectotypes are selected for all of the synonymous taxa of Eucrassatella.
There has been an overrecognition of full, cognate species between the Panamic and Caribbean
faunal provinces. Increased consideration should be given to the use of subspecies or describing the
morphological differences between populations without naming them.
The Caribbean Crassinella aduncata Weisbord, 1964, is related to the eastern Pacific C. adams: Olsson,
1961; C. maldonadoensis (Pilsbry, 1897) from Uruguay is very similar to the eastern Pacific C. nucu-
liformis Berry, 1940.
I HAVE PREVIOUSLY reviewed the members of the genus
Crassinella occurring in the eastern Pacific, a genus in the
crassatellid subfamily Scambulinae (CoAN, 1979). Here I
treat the subfamily Crassatellinae, which is represented
in the eastern Pacific by the genus Eucrassatella. In par-
ticular, I have addressed the appropriate generic alloca-
tion for eastern Pacific members of this subfamily and the
status of the subgenus Hybolophus; the validity of two taxa
recently described from Ecuador, Eucrassinella manabien-
sis and E. aequitorialis Cruz; the proper home for Cvas-
satella marginata Keep; the question of whether or not
Crassatella corbuloides Reeve is a synonym of the eastern
Pacific Eucrassatella gibbosa (Sowerby); the relationship of
the Plio-Pleistocene Crassatellites lomitensis Oldroyd to the
southern Californian Eucrassatella fluctuata (Carpenter);
and the relationship of the eastern Pacific Eucrassatella
diguet: (Lamy) to the Caribbean E. antillarum. This led
to consideration of how, in general, related taxa in the
Panamic and Caribbean faunal provinces are handled no-
menclaturally, and I have included here a discussion on
this topic.
I have also included some information that has recently
come to my attention about two western Atlantic species
of Crassinella that are related to eastern Pacific taxa.
The Crassatellidae is an ancient and conservative fam-
ily of marine bivalves, first appearing in the Paleozoic
(Boyp & NEWELL, 1968; CHAVAN, 1969; Morris, 1978).
The arrangement of its genera, including the Recent taxa,
is in a less-than-satisfactory state. Previous reviews of the
Recent crassatellid species of the world are by REEVE
(1842, 1843), Nyst (1847), TRYON (1872b), LOBBECKE
& KoOBELT (1881, 1886), and LAMy (1917). BERNARD
(1983:36) has recently listed the three eastern Pacific taxa
of Eucrassatella.
CONVENTIONS anp ABBREVIATIONS
In the following treatment, the correct name is followed
by a synonymy, information on type specimens and local-
ities, notes on distribution and habitat, and an additional
discussion.
Page 154
The synonymies include all major accounts about the
species, but not minor mentions in the literature. The
entries are arranged in chronological order under each
species-name, with changes in generic allocation and other
notes provided in brackets at the end of the entry.
The following are the abbreviations of institutions used
in the text:
AMNH—American Museum of Natural History
BM(NH)—British Museum (Natural History)
CASIZ—California Academy of Sciences, Department
of Invertebrate Zoology
CASGTC—California Academy of Sciences, Geology
Type Collection (numbers being replaced with CAS-
IZ numbers)
LACM—Los Angeles County Museum of Natural
History
USNM—United States National Museum of Natural
History
A “pair” means the two valves of one individual.
Family CRASSATELLIDAE Feérussac, 1822
Crassatellidae FERUSSAC, 1822:xxxix, xlii; as ““Crassatelles”
Subfamily Crassatellinae Férussac, 1822
Crassatella Lamarck, 1799
Crassatella LAMARCK, 1799:85-86; type species (monotypy):
““Mactra cygnea Chemnitz,’ LAMARCK, 1799 (non Mac-
tra cygnus GMELIN, 1791:3260, ex Chemnitz MS, a
Mactra), =Venus ponderosa GMELIN, 1791:3280, of
which both Crassatella gibba LAMARCK, 1801:119, and
C. tumida LAMARCK, 1805:408-409, are synonyms;
middle Eocene, Paris Basin
Crassatellites KRUGER, 1823:466 (unavailable; “ICZN Code,”
Arts. 20, 56b, because is based on Cvassatella and mod-
cee
ified only with an “ztes” ending to indicate fossil taxa)
There are no known living members of the genus C7as-
satella in the eastern Pacific, but the name has been used
for species in that province (as by MCLEAN, 1978:73), as
has the unavailable generic unit Cvassatellites Kriiger.
Species of Crassatella have an opisthodetic ligament con-
fined to the upper half of a broad hinge plate, and the
inner ventral margins of their valves are denticulate. Cras-
satella ponderosa (Gmelin, 1791) is not uncommon in the
middle Eocene of the Paris Basin, and the genus has been
reported from the Cretaceous to the Recent (CHAVAN,
1969:N573).
The nomenclatural thicket surrounding the type species
of Crassatella has been discussed by STEWART (1930:134-
136), and by VOKEs (1973:48-52), who said that he in-
tended to file a petition with the International Commis-
sion on Zoological Nomenclature about it, but none has
yet been published. Because it is a classic case of a mis-
identified type species, a petition would be required to
validate the formulation above (“ICZN Code,” Art. 70).
Species of Crassatella that occur in the Recent fauna are
The Veliger, Vol. 26, No. 3
Figure 1
Bathytormus radiata (Sowerby); Singapore; drawing of gross
anatomy after PELSENEER (1911). Note vertical orientation of
ctenidial axis. Approximately x 2.
placed into separate subgenera, including Indocrassatella
CHAVAN, 1952:119 (type species by original designation:
C. indica SMITH, 1895:265, of the Arabian Sea). HABE
(1981:110) now ranks /ndocrassatella as a full genus, in-
cluding in it 7. oblonga (YOKOYAMA, 1920:142-143: plt.
11, figs. 8, 9) from Japan. A second subgenus, Riosatella
VOKES, 1973:52, occurs in the western Atlantic. Its type
species, by original designation, C. (R.) riograndensis
VOKES, 1973 (pp. 52-57; plt. 1, figs. 1-5), seems to be a
synonym of C. (R.) brasiliensis (DALL, 1903a:101-102)."
Several fossil taxa from eastern North America are re-
ferred to Crassatella, and on the Pacific Coast C. washing-
toniana (WEAVER, 1912:32, plt. 4, fig. 42; plt. 5, fig. 51)
has been assigned here as well (STEWART, 1930:137). As
far as I know, none of these fossil taxa have been assigned
to subgenera, and the arrangement and ranking of the
named generic units near C7vassatella awaits careful study.
The anatomy of Crassatella (Indocrassatella) indica has
been briefly discussed but not illustrated by STOLICZKA
(1871:291-292), RIpDEwoopD (1903:223), and WHITE
(1942:64). PELSENEER (1911:37; plt. 13, fig. 1) discussed
and illustrated the external anatomy of another crassatel-
fig. 2) from Singapore, and that figure is copied here (Fig-
ure 1). Bathytormus is conspicuously different from C7vas-
satella indica and Eucrassatella (discussed below) in that
the ctenidial axis is oriented almost dorso-ventrally.
Eucrassatella Iredale, 1924
Eucrassatella IREDALE, 1924:181, 202; type species (original
designation): Crassatella kingicola LAMARCK, 1805:409,
from King Island, northwest of Tasmania
‘A still older name is possibly Crassatella uruguayensis SMITH,
1880 (pp. 321-322). Rios (1975:212) synonymizes C. riogran-
densis with C. uruguayensis, incorrectly terming Smith’s species
“invalid.”
E. Coan, 1984
Page 155
Hybolophus STEWART, 1930:139; type species (original des-
ignation): Crassatella gibbosa Sowerby!, 1832, from the
eastern Pacific, discussed below
Eucrassinella CRUZ, 1980:66 (unavailable, no designated type
species; “ICZN Code,” Art. 13b)
Eucrassatella was erected by IREDALE (1924) for some
Australian species that had previously been allocated to
Crassatella. He argued that neither Crassatella nor Cras-
satellites were available for nomenclatural reasons. DAR-
RAGH (1964, 1965a) has discussed the nomenclature and
distribution of E. kingicola and other Australian members
of this genus.
Members of Eucrassatella are medium-sized to large (to
over 100 mm), with an even outline to produced poste-
riorly in some. The beaks are inflated in some species and
flattened in others, and are prosogyrate to slightly opistho-
gyrate. The valves have prominent concentric folds, some-
times confined to the beaks but sometimes covering the
entire shell surface. There is a dark brown periostracum
in most species. Juvenile specimens are extraordinarily
flattened laterally in some species.
The attachment of the internal ligament extends from
the umbones almost to the ventral margin of the hinge
plate. There are two cardinal teeth anterior to the resilium
in the left valve and two in the right, although the anterior
cardinal may be almost obsolete in the right valve. The
cardinal teeth often have serrations on their anterior and
posterior surfaces. The right valve has an elongate pos-
terior lateral tooth that fits into a slot in the left valve; the
ventral margin of this slot is often raised into a tooth. The
left valve has an anterior lateral tooth that fits into a slot
in the right valve; the ventral margin of this slot is also
often raised into a tooth. DARRAGH (1965b) has discussed
the incidence of hinge transposition in Eucrassatella. The
pallial sinus is entire, and there are no denticulations along
the inner ventral valve margins.
The external anatomy of Eucrassatella was discussed by
WoobDwaRD (1854:300) and later illustrated by him
(WoopDwaRD, 1866:466; fig. 259). His figure is repro-
duced here (Figure 2). Woodward’s specimen was col-
lected at “Sandy Cape,” presumably in Queensland, and
was referred by him to E. pulchra (REEVE, 1842:43).?
RIDEWOOD (1903:223) later commented on the flat, homo-
rhabdic ctenidia of the Australian E. cuming: (A. ADAMS,
1854a:90-91; plt. 16, fig. 1).
* Because Sandy Cape is outside the reported distribution of
E. pulchra (see DARRAGH, 1964:8), the specimen discussed and
illustrated by Woodward may have been another species, per-
haps also E. cuming: (A. Adams). Eucrassatella corbuloides (REEVE,
1842:45), an Australian taxon not listed by Darragh, may be a
senior synonym of the latter (type: BM(NH) 1953.4.15.9, ho-
lotype; length, 44.0 mm; height, 34.4 mm; thickness, 23.9 mm).
Darragh (im litt., 2 March 1983) now thinks that E. cumingi, E.
pulchra, and E. decipiens (REEVE, 1842:42-43) may represent a
cline from Perth, Western Australia, along the coasts of North-
ern Australia and Queensland, to northern New South Wales.
Presumably, E. corbuloides would fit into this cline as well.
Figure 2
Eucrassatella “‘pulchra (Reeve); Sandy Cape, Queensland, Aus-
tralia; drawing of gross anatomy copied from WOODWARD (1866).
Approximately x 1.
Ridewood also said that he had studied the ctenidia of
Crassatella floridana DALL, 1881:131, now regarded as a
synonym of Eucrassatella speciosa (A. ADAMS, 1854b:94),
from the western Atlantic. The identity of the material,
which had been sent to him by Dall himself, was also
confirmed by E. A. Smith. Ridewood found the ctenidia
of the specimen to be strongly plicate and the foot to be
“relatively huge saltatory.” He suggested that these char-
acters were so unique that workers might choose to sep-
arate this species from other crassatellids. However, HARRY
(1966:86-87) recently examined a specimen of E. spe-
ciosa and found that the ctenidia are not pleated, leaving
doubt about the identity of Ridewood’s specimen. Harry
also described other features of the anatomy of EL. speciosa.
STEWART (1930) proposed Hybolophus as a subgenus of
Eucrassatella, with the eastern Pacific E. gibbosa as its type
species. The chief character he used to separate Hybolo-
phus from the Australian nominal subgenus was the sup-
posed opisthogyrate beaks of E. gibbosa, of “a large species
from Lower California,” and of E. antillarum. He said
that E. gibbosa was “distinctly opisthogyrate,” the Baja
Californian species was “‘slightly opisthogyrate,” and the
Caribbean E. antillarum was, simply, “opisthogyrate.”
West American fossil taxa, on the other hand, he said lack
backwards-pointing beaks.
Stewart also noted that the two living west American
forms he studied differed from Australian material in that
they had flattened umbones, but he also pointed out that
Eucrassatella kingicola has umbones that are not as inflated
as other Australian species of the genus. His somewhat
ambivalent conclusion was that “Although none of the
American species seem particularly closely related to Eu-
crassatella, 1 have not been able to discover any character
by which they may all be separated from the Australian
species.”
DarRRAGH (1965a:5), commenting on this question, said,
“Species from the Central American Region (California
to Peru and the West Indies) do not belong in Eucrassa-
tella but in Hybolophus. ... Hybolophus has opisthogyral
Page 156
or orthogyral umbones, a sinuous ventral margin, and
rather elongate anterior laterals.”
None of the characters mentioned by Stewart or Dar-
ragh seems to be an adequate basis for distinguishing an
eastern Pacific subgenus. The Californian Eucrassatella
fluctuata has inflated, prosogyrate beaks and a more-or-
less even ventral margin, and would thus have to be sep-
arately placed in E. (Eucrassatella), as would a number of
West Coast fossil taxa. The Australian E. cumingi some-
times has a sinuous posterior ventral margin (DARRAGH,
1964: plt. 2, fig. 9), and FE. corbulordes (REEVE, 1842:45)
has a still more sinuous posterior end.
I would not term the beaks of the Recent American
species of Eucrassatella strongly opisthogyrate. Those of
E. gibbosa are barely so, if at all. I would term those of
what we have called “E. digueti” (presumably Stewart’s
large Baja Californian species) slightly prosogyrate. The
beaks of the western Atlantic E. speciosa are flattened and
orthogyrate.
In contrast to Darragh’s claim, the anterior lateral of
E. gibbosa in the left valve and its corresponding socket in
the right valve are not conspicuously elongate. In fact,
CHAVAN (1969:N576) characterizes the difference be-
tween the two taxa as being quite the opposite—short
anterior laterals in Hybolophus and long anterior laterals
in Eucrassatella. The length of the anterior laterals is of
some use in separating species, however, as will be shown
below.’
Thus, the differences between the Australian species of
Eucrassatella and those of the eastern Pacific and western
Atlantic are not sufficiently great or consistent to merit
their subgeneric separation, and I regard Hybolophus as a
synonym of Eucrassatella. Perhaps when the living and
fossil taxa are studied in greater detail, two distinct lines
will be more apparent.
Eucrassinella was proposed by CRuz (1980) in combi-
nation with two new species. Both species are synonyms
of Eucrassatella gibbosa (see below), and because the genus
>Boyp & NEWELL (1968:10; 1969:N908-N911) call into
question the routine application of the Bernard and Munier-
Chalmas system of numbering bivalve hinge teeth, particularly
to the crassatellids, as by LAMy (1917), DARRAGH (1965a), and
CHAVAN (1969).
The Veliger, Vol. 26, No. 3
is proposed without the designation of a type species, it
must be regarded as unavailable (“IGZN Code,” Art. 13b).
The three eastern Pacific species of Eucrassatella may
be differentiated as follows:
(1) Anterior lateral in left valve (and socket for it in right
valve) elongate; posterior cardinal (just anterior to re-
silium) bifid, with a thin posterior lamella; beaks flat-
tened; distinctly truncate posteriorly... EF. antillarum
(2) Anterior lateral in left valve (and socket in right valve)
elongate; posterior cardinal not bifid, but with an in-
dented posterior platform; beaks not flattened; very
broadly and indistinctly truncate posteriorly .......
E. fluctuata
(3) Anterior lateral in left valve (and corresponding sock-
et in right valve) short; posterior cardinal in right
valve not bifid, with a flat posterior platform; beaks
flattened; narrow posterior ridge present rather than
a truncation as O86 so doat sng aS eee E. gibbosa
A word of caution: the most variable feature of species
of Eucrassatella is the degree of elongation of the posterior
end, and unusually elongate specimens may be encoun-
tered in both E. antillarum and E. gibbosa. Other features
are more reliable. Fossil taxa should be reexamined in
light of the variability in posterior length among Recent
material.
Eucrassatella fluctuata (Carpenter, 1864)
(Figures 3, 4, 5)
Astarte fluctuata Carpenter, 1864
CARPENTER, 1864b:611, 642 [1872:97, 128]
CARPENTER, 1866:209
TRYON, 1872b:246
SMITH, 1881:231
DALL, 1921:31 [Crassatellites]
OLpDROYD, 1925:109 [Crassatellites]
Burcu, 1944:8; Burcu, 1945:11 [Crassatella]
WOODRING, et al., 1946:81-82; 131 (plt. expl.); plt. 13,
figs. 1-8 [Eucrassatella}
PALMER, 1958:81; 332 (plt. expl.); plt. 7, figs. 5-7 [Eu-
crassatella|
MCLEAN, 1969:73-74; fig. 40-3 [repr. 1978] [Crassa-
tella]
Mount, 1974:38-40, 42-43; plt. 1, figs. 7-10 [C7vas-
satella]
BERNARD, 1983:36 [Eucrassatella (Hybolophus)|
Explanation of Figures 3 to 10
Figures 3 to 5: Eucrassatella fluctuata (Carpenter). Figure 3.
Lectotype (herein) of Astarte fluctuata Carpenter, length, 8.4
mm. Figure 4. Holotype of Crassatellites lomitensis Oldroyd,
length, 42.0 mm. Figure 5. Specimens from Catalina Island, Los
Angeles Co., Calif.; 10 m; lengths, 43.5 mm and 42.2 mm; LACM
64-26 (illustrated by MCLEAN, 1969, 1978: fig. 40-3).
Figures 6 to 10: Eucrassatella gibbosa (Sowerby). Figure 6. Lec-
totype (herein) of Crassatella gibbosa Sowerby, length, 59.3 mm.
Figure 7. Holotype of Crassatellites rudis Li, length, 46.9 mm.
Figure 8. Holotype of Eucrassatella gibbosa tucilla Olsson, length,
66.6 mm. Figure 9. Holotype of Eucrassinella manabiensis Cruz,
length, 13 mm; copied from Cruz (1980). Figure 10. Holotype
of Eucrassinella aequitorialis Cruz, 18 mm; copied from CRUZ
(1980).
Page 158
Crassatellites lomitensis Oldroyd, 1924
OLDROYD, 1924:10; plt. C
GRANT & GALE, 1931:271
WOODRING et al., 1946:81 [as a synonym of Eucrassa-
tella fluctuata]
Mount, 1974:37-44; plt. 1, figs. 1-6 [Crassatella]
Type material and localities:
A. fluctuata—USNM 819749, lectotype herein, a right
valve, from Calif. State Coll. 1060; length, 8.4 mm;
height, 6.5 mm; thickness, 1.6 mm (Figure 3). Carpen-
ter evidently had two right valves, so the specimen in
the USNM cannot be a holotype, as indicated by PALM-
ER (1958). The second specimen has not come to light
in either the USNM, or at the University of California
at Berkeley (David Lindberg, oral communication, 14
March 1983).
Catalina Id., Los Angeles Co., California (about
33°27'N; 118°28’W); 73 m; James G. Cooper; June 20-
26, 1863.
C. lomitensis—Univ. Calif. Riverside 6621/1, holotype, a
left valve; length, 42.0 mm; width, 33.7 mm; thickness,
11.7 mm (Figure 4). OLDROYD (1924) implied that the
type specimen included both valves but illustrated only
this left valve, and a right valve was not located by
Mount (1974).
Lomita Lime Quarry, southern part of Lomita, Los
Angeles Co., California (33°47'N; 118°20’W); Lomita
Mar]; lower Pleistocene; S. Maus Purple.
Description:
Small for genus, to 53.2 mm in length (LACM 89202;
off San Clemente Id., Calif.); shell trigonal to longer pos-
teriorly, length 1.26 times height (SD, +0.08; N = 11);
moderately inflated, thickness 0.58 times height (SD,
+0.04; N = 12); posterior end only slightly truncate, not
produced; beaks inflated, prosogyrate, with concentric un-
dulations that continue onto posterior slope; undulations
often confined to beaks, but sometimes over entire valve.
Lunule and escutcheon relatively short, shallow. Perios-
tracum dark; shell surface under periostracum with dark,
radial bands.
Left valve with a fairly thin posterior cardinal and an
elongate anterior lateral. Posterior cardinal of right valve
attached dorsally to anterior cardinal and with a postero-
ventral pocket, not bifid as in E. antillarum; elongate slot
present for anterior lateral of left valve. Hinge teeth not
conspicuously serrate, as in E. gibbosa and E. antillarum.
Pallial line curving more sharply upward at its poste-
rior end than that in E. gibbosa. Pit for pedal elevator
under beaks not as deep as that in E. gzbbosa.
The type specimen being a single juvenile valve, I have
illustrated here both valves of adult Recent specimens
(Figure 5).
The Veliger, Vol. 26, No. 3
Distribution and habitat:
From off Santa Rosa Id. (34°5’N; 120°2’W) (USNM
211883) and off Santa Cruz Id. (34°3'5”N; 119°57'30”W)
(LACM 68-128), Santa Barbara Co., to off Santa Cata-
lina Id. (33°25'30"N; 118°30'33”W)(CASIZ 036682) and
probably as far south as to off northwest end of San Cle-
mente Id. (about 33°N; 119°W) (LACM 89202), Los An-
geles Co., California; 10 to 320 m, with a mean depth of
88 m. No bottom types are recorded, but it probably oc-
curs among rubble. This species is rare, and I have seen
only 18 Recent lots.
It is recorded in the lower Pliocene of Los Angeles Co.
(WINTERER & DURHAM, 1962:302), the upper Pliocene
of Orange Co. (ZINSMEISTER, 1971:122; Mount, 1974:
41); and the lower Pleistocene of Los Angeles Co.
(OLDROYD, 1924:10; SCHENCK, 1945:513; WOODRING et
al., 1946:81-82), all in California.
Discussion:
Based chiefly on a single lot from off Catalina Island
(Univ. California Riverside 7279/1-3), MounrT (1974)
argued that the Recent Ewcrassatella fluctuata differs from
the Plio-Pleistocene E. lomitensis in that it has (1) a dif-
ferent profile, (2) higher, more pronounced beaks that are
closer to the anterior end, and (3) concentric sculpture
that is confined to the umbones. However, this species is
rare, and having examined most of the extant Recent ma-
terial in public collections, I have noted considerable vari-
ability in these features.
Some specimens have a more elongate posterior end,
but many shells are closer to triangular. Some specimens
have the undulating concentric sculpture confined to the
beaks, whereas it covers most of the shell in other material.
Mount also mentions but does not specify differences in
the hinge, but his excellent description of the hinge of “E.
lomitensis” fits Recent material of E. fluctuata as well.
In describing C7rassatellites lomitensis, Oldroyd said, “in-
ner margin crenulated.” I have seen no sign of crenula-
tions on the specimens I have studied, including the ho-
lotype.
BERNARD (1983:36) synonymizes “C7assatella margina-
ta Keep, 1888” with this species, terming it a nomen nu-
dum. It does not belong here, and this is discussed below.
Eucrassatella gibbosa (Sowerby, 1832)
(Figures 6 to 11)
Crassatella gibbosa Sowerby’, 1832
- SOWERBY!, in BRODERIP & SOWERBY!, 1832:56
REEVE, 1841:63; plt. 44, fig. 2
REEVE, 1842:45
REEVE, 1843:plt. 1, figs. 1a, 1b :
HANLEY, 1843:37; plt. 12, fig. 16; 1856:341
Nyst, 1847:122-123
C. B. ADAMS, 1852a:516 [1852b:292]
CARPENTER, 1857a:280, 297
E. Coan, 1984
CARPENTER, 1864a:30 [1872:204]
CARPENTER, 1864b:537, 620, 669 [1872:23, 106, 155]
NELSON, 1870:203; ?plt. 7, fig. 9 [in part; see OLSson,
1932:88]
TRYON, 1872b:250
LOBBECKE & KOBELT, 1881:8-9; plt. 3, figs. 3, 3a, 4;
KoBELT, 1886:41 (plt. expl.)
Lamy, 1917:218-219
HERTLEIN & STRONG, 1946:103 [Crassatellites (Hybo-
lophus)]
HERTLEIN & STRONG, 1955:181-182 [Crassatellites (H.)]
KEEN, 1958:82, 83; fig. 158 [Crassatella (H.)]
OLSSON, 1961:179-180; 498 (plt. expl.); plt. 25, figs.
1-1b [Eucrassatella (H.)|
PARKER, 1964:117, 159, 168; plt. 4, figs. 18a, 18b [Cras-
satella (H.)]
KEEN, 1971:104, 105; figs. 230 [Eucrassatella (H.)]
BERNARD, 1983:36 [E. (H.)]
[not to be confused with Crassatella gibba Lamarck, 1801:
119, or with C. gibbosula Lamarck, 1805:410-411]
Crassatellites rudis Li, 1930
Li, 1930:257; 286 (plt. expl.); plt. 3, figs. 16
PitsBry, 1931:429-430; 440 (plt. expl.); plt. 41, figs.
9, 10 [as a form of C. gibbosus]
PARKER, 1964:120, 159; plt. 5, figs. 20a, 20b [as both
Eucrassatella and as Crassatella (Hybolophus), in each
case as a form of gibbosa]
Eucrassatella (Hybolophus) gibbosa tucilla Olsson, 1932
OLSSON, 1932:88; 228 (plt. expl.); plt. 6, fig. 6
PILSBRY & OLSSON, 1941:56
Eucrassinella manabiensis Cruz, 1980
CRUZ, 1980:67-68, 72, 73; figs. 5, 6 [figs. 1 and 2 are
Eucrassatella antillarum]
Eucrassinella aequitorialis Cruz, 1980
CRUZ, 1980:68, 72, 73; figs. 3, 4, 7
Crassatella digueti Lamy, auctt., non Lamy, 1917
DuruHaM, 1950:70; 161 (plt. expl.); plt. 16, figs. 5, 13
Type material and localities:
C. gibbosa—BM(NH) 1953.4.15.15, lectotype herein,
pair, the larger specimen figured by REEVE (1843);
length, 59.3 mm; height, 44.5 mm; thickness, 31.4 mm
(Figure 6). The specimen was labeled “holotype,” but
it is clear that Sowerby had more than one specimen.
BM(NH) 1842.5.10.1586, probable paralectotype;
length, 41.5 mm; height, 25.9 mm; thickness, 19.3 mm.
Either Jipijapa [Puerto de Cayo], Manabi Prov.
(1°20'S; 80°45'W); or Santa Elena, Guayas Prov.
(2°11'S; 80°52’W), Ecuador, 20 m; sandy mud; Hugh
Cuming.
C. rudis—AMNH 22076, holotype, a right valve; length,
46.9 mm; height, 31.0 mm; thickness, 9:9 mm (Figure
7). The specimen was labeled “syntype,” but there is
no evidence of there having been any other specimens
in the lot (Batten, 27 /tt., 1 March 1983).
Mouth of Rio Grande [now the Panama Canal], near
La Bocca, about 1.6 km offshore, Panama Bay, Panama
(about 8°55'N; 79°33’W); 3-12 m; mud; Donald F.
MacDonald, 1907. “lower Miocene,” but really Re-
cent.
Page 159
E. gibbosa tucilla—Paleontological Research Institution
2197, holotype, a broken right valve; length, 66.6 mm,
height, 53.3 mm; thickness, 25.6 mm (Figure 8).
Quebrada Tucillal, Zorritos, Tumbez Prov., Peru
(3°40'S; 80°40'W); Tumbez Formation; upper Mio-
cene.
E. manabiensis—Mius. Biol. Mar., Inst. Oceanograf. de la
Armada, Guayaquil, Ecuador; holotype; pair; length,
13 mm; height, 8 mm; thickness, 2 mm (Figure 9; re-
produced from Cruz, 1980: figs. 5, 6). Paratypes,
USNM 768218 & 768219. The paratype illustrated in
Cruz’s figures 1 and 2 appears to be a juvenile of Hu-
crassatella antillarum.
Type locality not made clear in original publica-
tion, but according to Cruz (im litt., 23 March 1983)
the holotype came from Machalilla, Manabi Prov., Ec-
uador (1927'S; 80°46'W); between 11 and 17 m.
E. aequatorialis—Mus. Biol. Mar., Inst. Oceanograf. de
la Armada, Guayaquil, Ecuador; holotype, pair; length,
18 mm; height, 11 mm; thickness, 6 mm (Figure 10;
reproduced from CRUZ, 1980:fig. 7).
Machalilla, Manabi Prov., Ecuador (1°27’S;
80°46’W); on beach.
Description:
Medium-sized for genus, to 87.4 mm in length (CASIZ
036002; Guaymas, Sonora, Mexico); shell elongate, from
equilateral to longer posteriorly, length 1.45 times height
(SD, +0.09; N= 19); inflated, especially anteriorly,
thickness 0.67 times height (SD, £0.05; N = 19); poste-
rior end with a very narrow truncation, forming a sharp
ridge on many specimens; posterior end very produced in
some specimens; beaks flattened, orthogyrate to slightly
opisthogyrate, with prominent concentric folds that ter-
minate at posterior ridge; rest of surface with low, irreg-
ular growth lines. Lunule and escutcheon relatively short
and deep. Periostracum dark brown; shell surface under
periostracum brown, sometimes with dark radial rays.
Left valve with a short anterior lateral. Posterior car-
dinal of right valve rarely attached to anterior cardinal,
with a postero-ventral shelf, not bifid, as in E. antillarum;
short pocket present for anterior lateral of left valve. Hinge
teeth serrate, serrations larger than those in E. antillarum.
Pallial line curving evenly upward toward posterior ad-
ductor muscle scar. Pit for pedal elevator under beaks
unusually deep.
The soft parts (Figure 11) are similar to those of Eu-
crassatella “pulchra” (Figure 2).
Distribution and habitat:
Bahia San Juanico, outer coast of Baja California Sur,
Mexico (26°15'N; 112°27’20"W) (LACM 71-180),
throughout the Gulf of California, to Paita, Piura Prov.,
Peru (5°5’S; 81°7’W) (USNM 48447; OLsson, 1961:180);
5 to 110 m, with a mean depth of 32 m; most records
Page 160
Figure 11
Eucrassatella gibbosa (Sowerby); Puerto de la Concordia, Gua-
temala; 18 m; ANSP 317727. Sketch of positions of ctenidia,
palps, and foot. Approximately x 2.
suggest that the species occurs on sand bottoms, although
mud is also recorded at two stations. BERNARD (1983:36)
reports this species from the Galapagos Islands, but I have
not seen any material from there. This is the most com-
mon of the three species, and I have seen 167 Recent lots.
This species has been reported from the upper Miocene
of Peru (NELSON, 1870:203; OLsson, 1932:88) and from
the Pliocene of Ecuador (PILSBRY & OLSSON, 1941:56)
(the last two references as E. gibbosa tucilla); from the
Pleistocene of the Burica Peninsula in Panama (OLSSON,
1942:162) and of Bahia de Santa Inez, Baja California
Sur (DURHAM, 1950:70, as C. diguetz). It may also be
responsible for the record of “Crassatella n. esp. af. gib-
bosa” from the Pliocene of Punta Concepcion, Baja Cali-
fornia Sur (WILSON, 1948a:35; 1948b:1780).
Discussion:
PILsBRY (1931) was the first to recognize that Li’s Cras-
satellites rudis was actually from the Recent fauna, not
from the Miocene as Li had thought. It is nothing more
than a rostrate specimen of E. gibbosa.
Olsson’s claims for the uniqueness of E. g. tucilla are
that this subspecies is (1) larger, (2) less convex, (3) less
pointed posteriorly, and (4) has straighter, less contracted
postero-dorsal submargins. It is certainly not true that it
is larger, the largest Recent specimen being some 17 mm
longer than the largest specimens attributed to Olsson’s
subspecies. Large Recent specimens are generally both
less convex and less pointed, making their postero-dorsal
slope less convex.
The Veliger, Vol. 26, No. 3
Whereas Cruz’s new genus, Eucrassinella, is unavail-
able, his two new species are. However, both holotypes
are juvenile specimens of this species.
BERNARD (1983:36) has synonymized Crassatella cor-
buloides Reeve, 1842, with this species, but it is instead
from Australia (see footnote 2).
Crassatellites subgibbosus HANNA, 1926 (pp. 463-464;
500; plt. 28, figs. 1-4) from the Imperial Formation of
southern California may prove to be a synonym of Eu-
crassatella gibbosa. STANTON (1966:28-29; 24; plt. 5, figs.
9-12) reports E. subgibbosa from the upper Miocene Cas-
taic Formation, also in southern California, listing some
differentiating characters that I find unconvincing. How-
ever, the material available to me from either locality is
insufficient for a definitive conclusion to be drawn.
There are several other fossil taxa from the Americas
that may be related to this species, but it is beyond the
scope of this paper to determine which are closest or to
elucidate their nomenclature. Several of these were re-
cently discussed by WOODRING (1982:633-634).
Eucrassatella antillarum (Reeve, 1842)
(Figures 12 to 16)
Crassatella undulata Sowerby!, 1832; non Say, 1824; non
(Lamarck, 1801)
SOWERBY!, IN BRODERIP & SOWERBY!, 1832:56
REEVE, 1842:44
REEVE, 1843:plt. 1, figs. 2a, 2b
HANLEY, 1843:37; plt. 12, fig. 24; 1856:341
Nyst, 1847:128-129
CARPENTER, 1857a:297
TRYON, 1872b:251
LOBBECKE & KOBELT, 1881:11-12; plt. 4, figs. 3, 3a;
KOBELT, 1886:41 (plt. expl.)
[non Say, 1824:142; plt. 11, figs. 2]
[non Crassatella undulata (LAMARCK, 1801:120)]
Crassatella antillarum Reeve, 1842
REEVE, 1842:44-45
REEVE, 1843:plt. 2, fig. 8
HANLEY, 1843:37
Nyst, 1847:120-121
CHENU, 1862:131; fig. 623
TRYON, 1872b:248
LOBBECKE & KOBELT, 1881:7-8; plt. 3, figs. 1, 2, 2a;
KoBELT, 1886:41 (plt. expl.)
DALL, 1903b:1475 [Crassatellites]
Lamy, 1917:216-217; 202, figs. [Crassatella]
GRANT & GALE, 1931:271; 906 (plt. expl.); plt. 13, figs.
7a, 7b [Crassatellites]
WEISBORD, 1964:194-197; 514 (plt. expl.); plt. 25, figs.
9, 10 [Eucrassatella (Hybolophus)|
Explanation of Figures 12 to 16
Figures 12 to 16: Eucrassatella antillarum (Reeve). Figure 12.
Lectotype (herein) of C7assatella antillarum Reeve, length, 80.0
mm. Figure 13. Lectotype (herein) of C7assatella undulata Sow-
erby, length, 66.6 mm. Figure 14. Lectotype (herein) of Cras-
satella laevis A. Adams, length, 42.5 mm. Figure 15. Holotype
of Crassatella adelinae Tryon, length, 75.0 mm. Figure 16. Ho-
lotype of Crassatellites laronus Jordan, length, 77.5 mm.
E. Coan, 1984 Page 161
Page 162
GIBSON-SMITH & GIBSON-SMITH, 1979:28 [E. (H.)]
{note: ““antillarum” is a noun meaning “of the Antilles”
and thus does not change its ending with the gender
of the generic name.]
Crassatella rostrata Lamarck, auctt., non Lamarck, 1818
DELESSERT, 1841:plt. 4, figs. 2a, 2b, 3a, 3b
[mon LAMARCK, 1818:482 (LAMARCK, 1805:408, is a no-
men nudum), an Asian Bathytormus]|
Crassatella laevis A. Adams, 1854
A. ADAMS, 1854b:94
TRYON, 1872b:250
LOBBECKE & KOBELT, 1881:9-10; ?plt. 3, figs. 5, 5a;
KoBELT, 1886:37; 41 (plt. expl.)
Lamy, 1917:217
[not preoccupied by C. laevis HOENINGHAUS, 1831:162,
a nomen nudum]
Crassatella adelinae Tryon, 1872
TRYON, 1872a:130; plt. 6, figs. 1, 1a
TRYON, 1872b:249
WEISBORD, 1964:195, 197 [as a synonym of E. (H.)
antillarum|
Crassatella digueti Lamy, 1917; new name for C. undulata
Sowerby, 1932; non Say, 1824; non (Lamarck,
1801)
Lamy, 1917:217-218
HERTLEIN & STRONG, 1946:102-103 [Crassatellites (H.)]
KEEN, 1958:82, 83; fig. 157 [Crassatella (H.)|
OLSSON, 1961:180; 498 (plt. expl.); plt. 25, fig. 2 [as
Eucrassatella (H.) “diqueti’’|
KEEN, -1971:104, 105; fig. 229 [E. (H.)]
BERNARD, 1983:36 [E. (7.)]
Crassatellites laronus Jordan, 1932
JORDAN, 1932:9-10
JORDAN, 1936:124-125; 164 (plt. expl.); plt. 17, figs.
OG, i/
DuRHAM, 1950:70-71; 161 (plt. expl.); plt. 16, figs. 8,
14
HERTLEIN & STRONG, 1946:102 [as a synonym of C.
(H.) digueti]
Crassatella gibbosa Sowerby, auctt.; non Sowerby, 1832
KoBELT, 1886:34; 41 (plt. expl.); plt. 9, figs. 1
Eucrassinella manabiensis Cruz, 1980 [in part]
Cruz, 1980:72, figs. 1, 2
Type material and localities: -
C. undulata Sowerby—BM(NH) 1953.4.15.12, lectotype
herein, pair, probably the measured specimen and that
figured by REEVE (1843); length, 66.6 mm; height,
41.5 mm; thickness, 25.0 mm (Figure 13). BM(NH)
1953.4.15.12, a paralectotype; length, 23.4 mm; height,
14.2 mm; thickness, 7.4 mm.
Puerto Portrero, Guanacaste Prov., Costa Rica
(10°27’N; 85°48’W); 20 m; sandy mud; Hugh Cuming.
C. antillarum—BM(NH) 1953.4.15.10, lectotype herein,
pair, the measured syntype, which was figured by REEVE
(1843); length, 80.0 mm; height, 57.0 mm; thickness,
32.6 mm (Figure 12). BM(NH) 1953.4.15.11, a para-
lectotype; length, 82.3 mm; height, 56.4 mm; thickness,
27.3 mm.
Isla Margarita, Nueva Esparta, Venezuela (about
11°N; 64°W); “dredged up in the pearl-fisheries’;
Cuming Coll.
The Veliger, Vol. 26, No. 3
C. laevis—BM (NH) 1983.33/1-3, lectotype herein, pair;
length, 42.5 mm; height, 30.0 mm; thickness, 17.8 mm
(Figure 14). The lot also contains two paralectotypes,
one 31.4 mm in length, the other 27.7 mm in length.
Le Guaira, Federal Dist., Venezuela (10°36’N;
66°56’W); M. Le Marie; Cuming Coll.
C. adelinae—ANSP 55282, holotype, pair; length, 75.0
mm; height, 56.9 mm; thickness, 27.7 mm (Figure 15).
Locality unknown. WEISBORD (1964: 197) says, “The
habitat of Tryon’s E. adelinae was unknown when that
species was described in 1872, but it was subsequently
determined to be also from Margarita Island in Vene-
zuela.”
C. laronus—CASIZ 036680 (formerly CASGTC 5593),
holotype, a right valve; length, 77.5 mm; height, 54.6
mm; thickness, 12.8 mm (Figure 16).
West anchorage, near the salt works, Isla San Jose,
Baja California Sur (about 24°53’N; 110°35’W); CAS
Loc. 23809; on beach; Fred Baker.
Description:
Large for genus, to 105.2 mm in length (Paul Stillians
Coll., according to DRAPER, 1980: 25; Bahia de los An-
geles, Baja California Norte, Mexico); shell elongate, al-
most always longer posteriorly, length 1.49 times height
(SD, +0.09; N = 16); moderately inflated, thickness 0.59
times height (SD, +0.06; N = 16), less so than E. gibbosa;
posterior end with a broad truncation and a distinctly set
off posterior slope; posterior end produced in many spec-
imens, “pinched off” by an indentation in some; beaks
orthogyrate or very slightly opisthogyrate, with prominent
concentric folds which end at anterior margin of posterior
slope; rest of surface with low, irregular growth lines.
Lunule and escutcheon relatively shallow; lunule elongate
on most specimens. Periostracum dark brown; shell sur-
face under periostracum sometimes with dark brown ra-
dial bands; some specimens with radial bands broken into
brown chevrons; young specimens with flecks of brown.
Left valve with an elongate anterior lateral. Posterior
cardinal of right valve not attached to anterior cardinal,
but bifid, with a narrow ridge next to resilium (the pos-
terior cardinal of left valve fits between these two por-
tions); elongate pocket present for anterior lateral of left
valve. Teeth serrate; serrations finer than those in E. gib-
bosa.
Distribution and habitat:
Venezuela: from the west coast of the Peninsula de Pa-
raguana, Falcon (about 70°W), to Isla de Margarita,
Nueva Esparta (about 64°W) (J. Gibson-Smith, in litt.,
28 Dec. 1982); from 3 to 8 m, but presumably also oc-
curring somewhat deeper; sand. It is not common in the
Caribbean, and I have seen only 15 lots; Gibson-Smith
knows of 4 more lots.
Eastern Pacific: from Cabo San Lucas, Baja California
Sur, Mexico (20°8’N; 110°W) (LACM 66-12 & 66-14;
E. Coan, 1984
CASIZ 036001; USNM 3984 & 12586), throughout the
Gulf of California, to Playas, Guayas Prov., Ecuador
(2°39’S; 87°52'W) (CASIZ 033528); 5 to 206 m, with a
mean depth of 45 m; almost all recorded bottom types
indicate sand or gravel. This species is not as common as
E. gibbosa; 1 have seen 84 lots from the eastern Pacific.
This species is also known from the Pliocene of Vene-
zuela (WEISBORD, 1964:196-197; GIBSON-SMITH &
GIBSON-SMITH, 1979:28). The Gibson-Smiths suggest that
the Mare Formation material might be a recognizable
subspecies, differing from Recent specimens in being more
elongate, and in having a straighter postero-dorsal margin
and a more pointed anterior end.
In the eastern Pacific, this species has been reported as
a fossil from Baja California Sur—from the Pliocene or
Pleistocene of Santa Rosalia (GRANT & GALE, 1931) and
from the Pleistocene of Isla Coronado (DURHAM, 1950,
as Crassatellites laronus), Punta E] Pulpito (HERTLEIN,
1957:63, as Crassatella digueti); and Bahia Magdalena
(JORDAN, 1936, as Crassatellites laronus).
I am not certain which earlier fossil species is closest to
Eucrassatella antillarum. A possible candidate is E. nelsoni
(GRYZYBOWSKI, 1899:639; 663 (plt. expl.); plt. 19, figs. 2,
2a) from the Miocene of Peru (see OLSSON, 1932:87-88;
228; plt. 6, figs. 1, 4).
Discussion:
REEVE (1842, 1843) discussed Crassatella antillarum, and
noted that it was similar to C. undulata Sowerby but did
not offer any characters to separate the two. LOBBECKE &
KOBELT (1881) also stressed the similarity of these species
but failed to point to differentiating characteristics. GRANT
& GALE (1931) used the name Crassatellites antillarum for
Pacific Coast fossil specimens from Baja California.
After examining the material available to me, I am
unable to find features upon which eastern Pacific mate-
rial can be reliably separated. The average specimen of
Eucrassatella antillarum from the Venezuelan coast may
be more produced posteriorly than the eastern Pacific E.
digueti, a feature noted by LAMy (1917:217) in the ma-
terial he studied, but both long and short forms are found
in both provinces, and, in fact, the lectotype of C. undulata
Sowerby (Figure 13) is more produced posteriorly than is
the lectotype of C. antillarum (Figure 12).
Crassatella laevis A. Adams, 1854b, described from Ven-
ezuela, sounded as if it might be a synonym of this species,
so I borrowed the type material from the British Museum,
and it confirmed my suspicion. Adams gave no measure-
ments of his specimens and reversed the anterior and pos-
terior ends in his description.
With the Caribbean taxon comes the synonym Crassa-
tella adelinae Tryon, 1872, described from an unknown
locality and synonymized by WEISBORD (1964). Carib-
bean material was also illustrated as “C7vassatella rostrata
Lamarck” by DELESSERT (1841), but NysT (1847:126-
127), Lamy (1913:104; 1917:221-223; plt. 6, fig. 4), and
Page 163
others have demonstrated that this was an error and that
Lamarck’s species is really from Asia.
Crassatella undulata Sowerby, 1832, is a primary hom-
onym of C. undulata Say, 1824, from the Miocene of Vir-
ginia.* Crassatella digueti Lamy, 1917, was proposed as a
replacement name and thus has the same type specimens
as Sowerby’s species.
Crassatellites laronus Jordan, 1932, is unquestionably
another synonym. It was differentiated from Cvassatella
undulata Sowerby as being thinner and less rostrate and
as having a straighter postero-dorsal margin, character
states well within the range of variability of this species.
Some biogeographic comments:
There is great inconsistency in how various workers
nomenclaturally handle related taxa between the Carib-
bean and Panamic faunal provinces. For the most part,
populations in the two provinces that differ in only minor
ways morphologically are regarded as separate species,
which are properly termed “cognates” or “homologues.”
Sometimes the morphological differences are so minor that,
were the two populations to occur within a single prov-
ince, the differences would be regarded merely as varia-
tion within a single taxon. (In the case of Eucrassatella
antillarum, I have not been able to find sufficient differ-
ences between the populations in the two provinces to
regard the names involved as anything but synonyms.)
Intermediate paths are possible between the recognition
of full, cognate species and a single species with disjunct,
undifferentiated populations—(1) to use the subspecific
level, or (2) merely to describe the morphological differ-
ences between the populations without recognizing them
as separate taxonomic units.
Workers on marine mollusks have not often relied upon
the subspecific option across the Panama land barrier,
and, in general, few subspecies are recognized among ma-
rine mollusks, in part because the pelagic larvae of many
forms ensure wide distributions within habitable territory
as well as the liberal mixing of genetic material. Whereas
the trans-Panama situation meets the criterion of geo-
graphic separation required of most subspecies, its abso-
lute and long standing nature—3.1 million years, accord-
ing to KEIGWIN (1978)—has made some workers hesitant
*Tt is also a secondary homonym of C7assatella undulata (LA-
MARCK, 1801:120), which was first proposed in the genus Paphia
and later reassigned to Crassatella by LAMARCK (1805:408). La-
marck’s species is a synonym of Cvassatella contraria (GMELIN,
1791:3277), from West Africa.
° Earlier literature used the term “‘analogues,” which is clearly
a misuse of this word since it implies a lack of phylogenetic
relationship. There remains a tendency to search out and list
pairs of so-called cognates between the Panamic and Caribbean
faunal provinces without sufficient knowledge of the groups in-
volved, and I harbor doubts about a number of the cognate pairs
listed in the useful compilation of VERMEIJ (1978:269-278).
Page 164
The Veliger, Vol. 26, No. 3
about invoking subspecies. However, for many groups of
marine mollusks, this is not a very long time at all.
In two of the three cases in which I have previously
used subspecies among marine bivalves, there were rela-
tively sharp morphological breaks corresponding to geo-
graphic constrictions, and I concluded that gene flow was
significantly restricted at those points. The third case in-
volved an 1300-km gap between morphologically differing
populations. Subspecies have sometimes been used in the
eastern Pacific for isolates on offshore islands.
The key decision that a systematist must make is whether
or not, in the absence of experimental evidence or other
direct measures of genetic divergence, interbreeding and
gene flow are occurring or could occur between popula-
tions. Judgments about this often have to be made on a
case-by-case basis by means of analogies about the system-
atic importance of morphological differences among other
species in the genus or family involved. This is, of course,
indirect evidence, and the marine mollusks have many
examples both of species within single genera that are
scarcely distinguishable morphologically and of single
species with astounding ranges of variability.
With regard to the Panama marine barrier, a decision
to recognize two species may almost be regarded as a
conclusion about the world as it is, with workers arguing
that reproductive isolation exists between two populations
that have significant morphological differences. This is in
contrast to a decision to recognize a pair of subspecies, a
decision that could be regarded as being a shade closer to
a conclusion about the world as it might be, with workers
arguing that reproductive isolation would not be complete
were gene flow once again to be possible between the two
differing populations. Thus, the seemingly absolute geo-
graphic separation across Panama may unjustifiably force
conclusions in favor of separate species; one can know that
gene flow is now impossible, whereas it is more difficult
to assume that it could take place. With more careful
studies on various groups, workers may want to give in-
creased consideration to the use,of subspecies for these
divergent populations, or merely to describe the morpho-
logical differences without providing names.
Crassatella marginata Keep, 1887, ex Carpenter. MS
A debate has continued for many years as to whether
this name was validated by Keep and about what it is.
BERNARD (1983:36) has recently termed it a nomen nu-
dum, dated it from 1888, and synonymized it with Eu-
crassatella fluctuata.
The name is validated in KEEP’s 1887 edition (p. 179).
Here is the entire entry: “Cvassatella marginata, Cpr., Cras-
sa-tel’-la mar-gin-a’-ta. Shells minute, about the size of
large pinheads; somewhat triangular; yellowish, marked
with chevrons of brown.” A later version of this work
(KEEP, 1904) adds that the species is ‘‘southern” (p. 50),
and that it was “described in this book” (p. 281).
Although this description is sparse, and although Keep’s
original specimens have not come to light in the parts of
his collection now housed in the California Academy of
Sciences and in the University of California at Berkeley
(Barry Roth and David Lindberg, verbal communica-
tions, Jan. 1983), I think that this taxon is recognizable.
There is but one genus with an internal ligament occur-
ring in southern California that fits this description, Halo-
dakra, a member of the Bernardinidae. It may be H. sal-
monea (Carpenter, 1864b), which was originally proposed
in the homonymous venerid genus Psephis with a still
more meager description (CARPENTER, 1864b:539, 611,
641; see also BERNARD, 1983:49). I am currently studying
the Bernardinidae, and the relationship of Halodakra sal-
monea to the tropical eastern Pacific type species of the
genus, H. subtrigona (CARPENTER, 1857b:82), is not yet
clear. It is possible that there may be two species in south-
ern California.
Keep initially credited his species to Carpenter, but
Carpenter never proposed it. What evidently happened is
this. When early collectors in southern California found
some specimens of Halodakra, they were sent to Carpenter
for identification. Perhaps forgetting all about his Psephis
salmonea, he thought that the specimens might be another
member of the Bernardinidae that he had already named
from Mazatlan, Circe margarita CARPENTER, 1857b:81,
now assigned to the genus Bernardina (KEEN, 1968:394,
395; fig. 4; BERNARD, 1983:49). Evidence for this comes
from a label by Carpenter filed with some specimens of
Halodakra from San Diego that had been in the Stanford
University Collection (now CASIZ 036681). The label
says, in part, ““?Crassatella margarita, Cpr., Maz Cat 114.
... Call it ?Crassatella; (not Circe).” Somewhere along the
way to Keep, the “margarita” evidently was mistranscribed
as “marginata.”
Subfamily Scambulinae Chavan, 1952
Scambulinae Chavan, 1952:120
Some comments on C7rassinella:
In my discussion of Crassinella adams: Olsson, 1961
(Coan, 1979:8), I mentioned Olsson’s reference to a sim-
ilar, undescribed Caribbean species, which he had seen
from Panama (OLSSON, 1961:183). I have not encountered
any material from the Caribbean coast of Panama, but I
think what Olsson may have had is C. aduncata WEIS-
BORD, 1964 (pp. 197-199; 514; plt. 25, figs. 11-14), de-
scribed from the Pliocene Mare Formation of Venezuela.
GIBSON-SMITH & GIBSON-SMITH (1979:28) report this
species from the Recent fauna of Venezuela,° and I have
seen specimens I tentatively assign to this species from
Jamaica (LACM 74-77). It differs from the eastern Pa-
6 They also show that C7vassinella triquetra WEISBORD, 1964
(pp. 199-200; 515; plt. 25, figs. 1, 2) is the same thing.
E. Coan, 1984
Page 165
cific C. adamsi in attaining a larger size, having a more
abrupt posterior slope, and in possessing more prominent
concentric ribs. A Recent Venezuelan lot of C. aduncata
has been placed in the California Academy of Sciences
through the courtesy of Jack Gibson-Smith (CASIZ
033530).
A western Atlantic cognate of another eastern Pacific
Crassinella has also come to my attention. It is C. maldona-
doensis (PILSBRY, 1897:295-296) described from Uru-
guay, which is very similar to the eastern Pacific C. nu-
culiformis Berry, 1940. This Atlantic species has been
discussed and illustrated by CASTELLANOS (1970:178-180;
figs. 5-10) and by SCARABINO (1977:205, 284-285; plt.
11, fig. 2). The type specimens are in the ANSP (#70522).
This species, which has been reported from Uruguay to
the Golfo San Matias, Argentina, is more pointed and
produced postero-ventrally and has a shorter escutcheon
than C. nuculiformis. Its umbones are less prominent, with
concentric ribs that fade out more quickly toward the ven-
tral margin. Thanks to the courtesy of Dr. James Mc-
Lean, specimens of this uncommon species have been
placed in the California Academy of Sciences (CASIZ
036827).
ACKNOWLEDGMENTS
I would like to express my appreciation to a number of
persons who helped me complete this project. I thank the
following personnel and curators who made material in
their institutions available for my study: Mary A. Gar-
back of the Academy of Natural Sciences of Philadelphia,
William K. Emerson and Roger Batten of the American
Museum of Natural History, Solene Morris of the British
Museum (Natural History), Barry Roth and Robert Van
Syoc of the California Academy of Sciences, James H.
McLean of the Los Angeles County Museum of Natural
History, Peter Hoover of the Paleontological Research
Institution, Kenneth Boss of the Museum of Comparative
Zoology at Harvard University, Joseph Rosewater of the
United States National Museum of Natural History, Da-
vid Lindberg of the University of California at Berkeley,
and Takashi Okutani of the National Science Museum of
Japan. I also acknowledge the specimens provided for study
by Manuel Cruz P., Jack Gibson-Smith, and Carol Skog-
lund. I appreciate the advice of Frank Bernard, Thomas
A. Darragh, Peter Rodda, and Harold Vokes, and the
comments on the manuscript by Kenneth Boss, Myra Keen,
James McLean, and Barry Roth. Dr. Roth was also of
invaluable assistance in obtaining the photographs needed.
LITERATURE CITED
All works cited in the text, including sources of taxonomic
units are listed. Volume, bulletin, monograph, memoir,
professional paper, and special paper numbers are in bold
face; series numbers, in parentheses, precede volume num-
bers; issue numbers, in parentheses, follow volume num-
bers; supplementary information, such as second methods
of listing volumes, part numbers, and parenthetical state-
ments, are given in brackets. Plates and portraits are list-
ed, but not text figures, maps, charts, and tables. Exact
publication dates are given when possible, as well as the
sources of this information if not from the publication
itself.
ADAMS, A. 1854a. Descriptions of new shells, from the Cum-
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ADAMS, A. 1854b. Descriptions of a new genus, and of several
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May 1854).
ADAMS, C. B. 1852a. Catalogue of shells collected at Panama,
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ADAMS, C. B. 1852b. Catalogue of shells collected at Panama,
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BERNARD, F. R. 1983. Catalogue of the living Bivalvia of the
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Berry, S.S. 1940. New Mollusca from the Pleistocene of San
Pedro, California—I. Bull. Amer. Paleo. 25 (94A):1-18
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BOURGUIGNAT, J.-R. 1925. Dates des livraisons de |’ Histoire
des Mollusques des Ferussac et Deshayes, vérifiées d’aprés
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Boyp, D. W. & N. D. NEWELL. 1968. Hinge grades in the
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BRODERIP, W. J. & G. B. SowerBy!. 1832. [... the new species
of Mollusca and Conchifera collected by Mr. Cuming, .. . .]
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Burcu, J. Q. (ed.). 1944. Family Crassatellidae, pp. 8-10, Jn:
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Conch. Club Southern California, Minutes 39:29 pp. (Sept.
1944).
Burcu, J. Q. 1945. Index, pp. 1-20, Jn: same. Conch. Club
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CARPENTER, P. P. 1857a. Report on the present state of our
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CARPENTER, P. P. 1857b. Catalogue of the collection of Ma-
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CARPENTER, P. P. 1864a. Review of Prof. C. B. Adams’s ‘Cat-
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Page 166
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CARPENTER, P. P. 1864b. Supplementary report on the present
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Florida with especial reference to the Silex beds of Tampa
and the Pliocene beds of the Caloosahatchie River including
in many cases a complete revision of the generic groups
treated and their American Tertiary species. Pt. 6. Con-
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Férussac, A. E. J. P. J. F. DA. 1821-1822. Tableaux sys-
tématiques des animaux mollusques classés en familles na-
turelles, dans lesqueles on a établi la concordance des tous
les systémes; suivis d’un prodrome général pour tous les
mollusques terrestres ou fluviatiles, vivants ou fossiles; ....
Paris (Bertrand) & London (Sowerby) 111 + 27 + xlvili
pp. [There are three collations of this work: SHERBORN &
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seems to be the case:
livr. 9—pp. 1-32 (?)—6 April 1821
livr. 10—33-40; 49-56—26 May 1821
livr. 11—57-80—13 July 1821
livr. 12—41-48; 81-96—21 Sept. 1821
livr. 13—97-111—10 Nov. 1821
livr. 14—i-xxiv—16 Feb. 1822
livr. 15—xxv-xlviii—13 April 1822
livr. 16—1-27—16 July 1822
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Page 167
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The Veliger 26(3):170-178 (January 3, 1984)
THE VELIGER
© CMS, Inc., 1984
Description of Five New Species of
Hawaiian Eulimidae
ANDERS WAREN
Department of Zoology, Box 25059, S-400 31 Goteborg, Sweden
BEATRICE L. BURCH anp THOMAS A. BURCH
236 Kuuhoa Place, P.O. Box 309, Kailua, Oahu, Hawaii 96734
Abstract. Five new species of Hawaiian Eulimidae are described. T7ochostilifer entospinea lives in
galls in spines of Chondrocidaris gigantea, T. hawatiensis in galls in the test of Prionocidaris hawaiiensis;
Vitreolina hawatiensis lives on the external surface of P. hawaiiensis, V. chondrocidaricola lives on
and inside Chondrocidaris gigantea, and Pelseneeria hawauensis lives attached to the gonopores of
Aspidodiadema hawauensis (all hosts Echinoidea). A second species of Pelseneeria is recorded, but not
described, from Stereocidaris hawatiensis.
INTRODUCTION
THE SPECIES OF THE family Eulimidae are almost exclu-
sively parasitic on echinoderms and constitute a large group
of gastropods in the tropical parts of the Indo-Pacific area.
The species live as endo- or ecto-parasites, and many ad-
aptations to a parasitic life are found in the group (WAREN,
in press). Comparatively few species are known from the
Hawaiian Islands (Kay, 1979; WAREN, 1980a, b, 1981),
but scattered records in the literature (SCHOENBERG, 1980)
and examination of museum collections show the diversity
of the family to be much greater than presently known.
We will here describe five new species that two of us
(B.L.B. & T.A.B.) have found during offshore dredgings
around the Hawaiian Islands.
The types and some additional specimens have been
deposited in the U.S. National Museum, Division of Mol-
lusks (USNM); the remaining specimens are in our col-
lections.
Trochostilifer Waren, 1980
Type species: T7ochostilifer domus Warén, 1980.
Remarks: Three species have previously been described
in this genus. Two live in galls in the spines and one on
the test of different cidaroid sea urchins (WAREN, 1980b).
The new species described below from Chondrocidaris gi-
gantea was mentioned by WAREN (1980b) but not de-
scribed.
Trochostilifer entospinea
Waren, B. Burch & T. Burch, spec. nov.
(Figures 3, 4, 5, 6, 8, 21)
Type material: Holotype, one female, USNM 792378;
paratype, the male from the same gall, USNM 792379.
Type locality: From a gall in a spine of Chondrocidaris
gigantea (A. Agassiz), 10 Feb. 1980, 21°25.8'N,
157°43.3’W, 18 m, Kailua Bay, Oahu, Hawaii (1 gall
with one female 2.53 mm, 1 male 1.0 mm, no egg cap-
sules).
Material examined: One single female, 2.40 mm high,
no egg capsules, 9 Dec. 1979, 21°25.8'N, 157°43.3'W, 15
m, Kailua Bay, Oahu, Hawaiian Islands, in a gall in
spines of Chondrocidaris gigantea; 1 spine from Chondro-
cidaris gigantea with 1 gall with a female, a male
and egg capsules, 1 small, empty gall (Figure 8), 13 Jan.
1980, 21°28.0’N, 157°43.0’W, 23 m, Maku manu, Oahu,
Hawaiian Islands, (spine saved intact); 1 spine with 1
female, 1.56 mm, 1 male, 0.80 mm, no egg capsules, 2
spines, each with a healed gall, no cavity or snail inside,
13 Jan. 1980, 21°26’N, 157°43’W, 15 m, Mokua Rock,
Oahu, Hawaiian Islands; 1 spine with a gall containing
1 female, height 3.04 mm, 1 male (crushed) and a dozen
egg capsules, 3 Feb. 1980, 1 very young specimen with
less than half a postlarval whorl, in a small pit beside a
gall, 21°19.5'N, 158°08.4’W, 15 m, Barbers Point, Oahu,
A. Waren et al., 1984
Page 171
Hawaiian Islands; 1 gall in a spine, from the type locality,
serially sectioned into 10 um sections, stained with Ehr-
lich’s haematoxylin-eosin, containing 1 male, 1 female,
several egg capsules, 1 very young specimen with less than
one half postlarval whorl, found in a small pit on the
outside of the same gall; 1 empty shell in shell sand, NW
end of Lanai Island, Hawaiian Islands; 20°55'N,
157°03'W, 20 m, Los Angeles County Museum 74-67.
Description—Female: Shell small, grayish transparent,
broadly conical with a flat base and mucronate larval shell.
The larval shell (Figure 21) is 390 um high and consists
of about 3.2 distinctly convex whorls. The holotype has
3.5 slightly concave postlarval whorls with a faint shoul-
der just below the suture. The body whorl is abruptly
rounded at the periphery and there is a well delimited
basal surface. The sculpture consists of about 15 rather
distinct spiral cords above the periphery and about 18 less
distinct and slightly undulating spiral lines on the basal
surface. There is also an axial sculpture of rather sharp
incremental lines of varying strength, running all the way
from the suture to the columella. The aperture is squarish
with the lower part retracted rather far behind its upper
parts. The outer lip is thin and very slightly flexuous (seen
from the side).
Dimensions of holotype: Height of the shell 1.68 mm,
maximum diameter 2.53 mm, minimum diameter 2.22
mm. (The dimensions of the aperture are irrelevant be-
cause they cannot be well defined.)
Male: Much smaller, up to 1.2 mm (approximate, spec-
imen crushed), with up to 1.3 postlarval whorls. Its shell
is more rounded and has a much less distinct sculpture
than the female.
Anatomy: The quality of the fixation of the two adult
specimens sectioned in situ in a spine did not allow any
detailed examination of the anatomy, but it could be seen
that the female has eyes, foot, large pedal folds, operculum
and a large proboscis. The proboscis was buried in the
tissues of the spine, 7.e., the wall of the gall. At this point
the tissues of the spine had a much higher content of
organic matter, judging from the higher absorption of the
stain (Ehrlich’s haematoxylin-eosin), than the other parts
of the gall and the spine. Therefore, we assume that ir-
ritation by the parasite causes a wound-like growth zone
here, which is used by the parasite. The precise way of
feeding can only be determined when better fixed material
is available.
Reproduction: The gall with the largest female (3.04
mm) contained about a dozen egg capsules. They are
spherical, have a single, simple, smooth wall, a diameter
of about 1 mm, and are attached by a short stalk. They
contain 150-200 young each, in different stages of devel-
opment. The diameter of uncleaved eggs is 100 um, the
height of the shell of the veliger larvae ready to hatch is
180 um. Thus, the species has planktotrophic development
because the height of newly settled larvae is 500 um.
Remarks: The shape of the shell of 7. entospinea resem-
bles most closely that of 7. domus Warén, 1980, but 7.
entospinea has a more distinctly angulated periphery than
T, domus and also a more pronounced spiral sculpture.
The other known species of Trochostilifer that live in galls
have a much less distinct spiral sculpture and also flatter
larval whorls. From 7. hawatiensis it can be separated
by the rounder periphery and the less distinct spiral sculp-
ture in that species.
Two spines (see material examined) had galls that ev-
idently were in the process of healing. The outer shape
and surface structure was typical for galls, but the cavity
had been filled in with calcium carbonate of a slightly
more spongy structure than the remaining parts of the
spine. One gall contained 2 empty shells, without any
visible damage, but no repair could be observed. These
observations suggest that the parasite has a shorter life
span than the host.
The first part of the postlarval shell in female 7. en-
tospinea, as in all other gall-producing species of T7o-
chostilifer that have been examined, starts with about one
third of a whorl which is completely smooth and quite
different from the later postlarval female shell. This part
of the shell is identical with that of a very young male,
and may possibly indicate that the specimens pass through
a more or less male phase. WAREN (1980b) sectioned a
very young solitary specimen that did not show any sexual
characteristics in the anatomy. Therefore, we believe that
this difference in postlarval sculpture reflects evolution
from earlier protandrous hermaphroditism.
Trochostilifer hawauensis
Waren, B. Burch & T. Burch, spec. nov.
(Figures 1, 2, 7, 9, 10, 20)
Type material: Holotype, a female, USNM 792376;
paratype, a male, USNM 792377.
Type locality: From a gall in the test of Prionocidaris
hawanensis (A. Agassiz), 18 Sept. 1980, 21°34.1'N,
157°49.3'W, 72 m, off Kaoio, Oahu, Hawaiian Islands.
Material examined: The type specimens, from 1 gall and:
1 female, 2.6 mm, 1 male, 1.48 mm, 17 egg capsules in
another gall from the same host species and the type lo-
cality.
Description—Female: Shell small, grayish transparent,
broadly conical, with a rounded base and styliform larval
shell. The larval shell (Figure 20) is about 450 um high
(measured from the intersection of its outer lip and the
first postlarval whorl), consists of about 3.2 almost flat
whorls, and is very obliquely inserted. The holotype has
a little more than 2.5 postlarval whorls, which are very
slightly convex. The suture is rather deep and distinct,
slightly channeled and made more distinct by the subse-
quent whorl joining at a right angle. The sculpture con-
A. Waren et al., 1984
Page 173
poe Dae SS ae
Explanation of Figures 8 to 10
Figure 8. Trochostilifer entospinea, galls (openings indicated by
arrows) in spine of Chondrocidaris gigantea. Total length of spine
20.5 mm.
sists of distinct, sharp, close-set incremental lines of vary-
ing strength. There is also a spiral sculpture, more distinct
on the basal surface, of broad but very indistinct ribs (more
visible in light that shines parallel to the surface of the
Figure 9. Male of 7. hawauensis, crawling, x 21.
Figure 10. Female and male of 7. hawaiiensis. P, pedal fold;
T, tentacle. x 10.
shell). The periphery of the body whorl is evenly rounded,
leaving the distinctly convex basal surface without any
sharp demarcation. The aperture is rather rounded. Seen
from the side, the outer lip is very slightly flexuous.
Explanation of Figures | to 7
Figure 1. Trochostilifer hawatiensis. Adult female diameter 3.0
mm.
Figure 2. 7. hawatiensis. Adult male, height 0.86 mm.
Figure 3. 7. entospinea. Adult female, diameter 2.5 mm.
Figure 4. 7. entospinea. Adult male, height 1.42 mm.
Figure 5. Newly settled 7. entospinea, height 0.62 mm.
Figure 6. 7. entospinea, apex. Scale line = 0.1 mm.
Figure 7. 7. hawatiensis, apex. Scale line = 0.1 mm. In Figure
6 and 7, a indicates the transition from planktotrophic to benthic
life, b the change to typical female growth.
The Veliger, Vol. 26, No. 3
Page 174
A. Waren et al., 1984
Dimensions of holotype: Height of the shell 2.30 mm,
maximum diameter 2.48 mm, minimum diameter 2.12
mm.
Male: Much smaller, maximum height 1.56 mm, shell
evenly rounded and almost without a trace of spiral sculp-
ture.
Soft parts: The male (Figures 9, 10) has a functional foot,
large flat, rather pointed tentacles with eyes placed cen-
trally in their bases. One large epipodial fold from each
side of the foot covers the base of the shell. Proboscis
probably retractile, because it could not be seen when the
male was crawling. The female (Figure 10) has fiat,
squarish tentacles, the tips of which very abruptly become
more slender and with small, black eyes (diameter 60 um
when preserved) centrally in the base of the tentacle. The
right epipodial fold is much larger than the left. The foot
is small but evidently functional and equipped with an
operculum. The proboscis of living females was not ob-
served.
Reproduction: One gall with a female of 2.6 mm height
and a male contained 17 egg capsules. Each capsule has
a short stalk, a smooth, simple wall and is evenly rounded
with a diameter of 0.8 mm (uncleaved eggs) to 1.2 mm
(veligers ready to hatch). The capsules contain about 150
eggs each. The diameter of the eggs is about 120 um; the
height of the shell of the veligers about 180 um. The size
of the veligers compared to the size of the larval shell
clearly indicates that 7. hawauensis has planktotrophic
larval development.
Remarks: 7. hawaziensis resembles 7. mortenseni Wa-
rén, 1980 in having a very faint spiral sculpture, but that
species has flatter whorls and a suture that is less well
marked than 7. hawauiensis.
Vitreolina Monterosato, 1884
Type species: Eulima incurva Renieri in Bucquoy,
Dautzenberg & Dollfus, 1883, subsequent designation,
Bucquoy, Dautzenberg & Dollfus, 1898.
Remarks: The type species is probably a parasite of some
ophiuroids, and originates from the Mediterranean. We
are convinced that the two species described below do not
belong to Vitreolina but should be classified in a new ge-
nus; lack of soft parts has made us hesitate to describe a
Page 175
new genus for them. We have, therefore, placed them in
Vitreolina provisionally, because of some similarity in shell
characters.
Vitreolina hawatiensis
Waren, B. Burch & T. Burch, spec. nov.
(Figures 15, 16, 17, 19)
Type material: Holotype (a female) USNM 792381 and
a paratype (a male) USNM 792382.
Type locality: Found on Prionocidaris hawauensis, 18 Sept.
1980, 21°34.1’N, 157°49.3’W, 72 m, off Kaoio, Oahu,
Hawaiian Islands.
Material examined: The type material and: 1 female,
2.20 mm, from Prionocidaris hawauensis, 8 Sept. 1980,
21°33.5'N, 157°49.0’W, 72 m.
Description—Female: Shell small, conical, slightly
curved, vitreous and slender, with numerous, slowly in-
creasing whorls. The larval shell consists of a little more
than 3 whorls and its height is 450 um. Its whorls are
colorless, perfectly transparent, and very slightly convex.
The holotype has 5.5 postlarval whorls which are almost
flat, except for the body whorl which is quite inflated.
The suture is very indistinct and the false suture (the line
marking the internal connection of the whorls) is much
more conspicuous. There are 4 incremental scars after the
one that marks the connection of the larval and postlarval
shells, placed slightly more than one whorl apart. The last
of these scars marks the point where the whorls become
inflated. The aperture is low and rounded, distinctly
broader in its lower part. Seen from the front, the outer
lip is slightly flexuous; seen from the side it is retracted
at the suture, strongly projecting below this, then retracted
again, in its lower part. The most projecting part is sit-
uated just above the upper third.
Dimensions of holotype: Height of the shell 3.48 mm,
diameter 1.40 mm, height of the aperture 1.04 mm, breadth
0.60 mm.
Male: Shell smaller (1.8 mm high), body whorl not in-
flated.
Soft parts: Not studied, but the general coloration of the
live animal is evenly yellowish to reddish brown.
Explanation of Figures 12 to 19
Figures 12, 13. Vitreolina chondrocidaricola, female.
Figure 14. V. chondrocidaricola, male, drawn at the same scale.
Figures 15, 16. V. hawaiiensis, female.
Figure 17. V. hawatiensis, male, drawn at the same scale.
Figure 18. V. chondrocidaricola, apex.
Figure 19. V. hawaiiensis, apex. The uppermost labial scars in
Figures 18 and 19 mark the change from planktonic to benthic
life.
Scale lines: Figures 12 to 17, 0.5 mm; Figures 18 to 19, 0.25
mm.
Page 176
The Veliger, Vol. 26, No. 3
Remarks: The specimens were found on the spines and
test of the host. The precise nature of the parasitism is
not known and because of the small number of specimens,
we did not want to break a shell to examine the soft parts.
Vitreolina chondrocidaricola
Waren, B. Burch & T. Burch, spec. nov.
(Figures 12, 13, 14, 18)
Type material: Holotype (a female) USNM 792383 and
8 paratypes USNM 792384.
Type locality: From the intestine of Chondrocidaris gi-
gantea, 9 Dec. 1979, 21°25.8'N, 157°43.3'W, 15 m, Kailua
Bay, Oahu, Hawaiian Islands.
Material examined: The type material and: 3 specimens,
from spines of C. gigantea, 13 Jan. 1980, 21°28.0'N,
157°43.0’'W, 23 m, Maku Manu, Oahu, Hawaiian Is-
lands, USNM 792385; 2 specimens from dorsal spines of
C. gigantea, 3 Feb. 1980, 21°20.5’N, 158°08’W, 23 m,
Kahe Point, Oahu, Hawaiian Islands, USNM 792386;
39 specimens from spines, 6 young and crushed specimens
from coelomic cavity of C. gigantea, 10 Feb. 1980,
21°25.8'N, 157°43.3’W, 18 m, Kailua Bay, Oahu, Hawai-
ian Islands; 8 specimens from dorsal spines of C. gigantea,
9 March 1980, Pilokahe Point, Oahu, Hawaiian Islands,
18 m, USNM 792387.
Description—Female: Shell small, colorless, transparent,
rather broadly conical, straight or slightly curved. The
larval shell consists of about 4 slightly convex, colorless
whorls with a distinct suture. The height is about 480 um.
The holotype has 4 postlarval whorls, which are less con-
vex than the larval whorls, perfectly smooth and with a
false suture more distinct than the real suture which is
shallow and inconspicuous. There are 3 incremental scars
in the holotype, at intervals of a little more than 1.0 whorls.
The aperture is low and rounded, deeply excavated in its
lower part. The outer lip is retracted at the suture and
evenly curved and projecting below this with its most pro-
truding part situated at the midpoint of its height (seen
from the side).
Dimensions of holotype: Height of the shell 2.10 mm,
diameter 0.86 mm, height of the aperture 0.64 mm, breadth
0.40 mm.
Male: Half the size of the female and with correspond-
ingly fewer whorls.
Soft parts: Not studied, but from a photograph it can be
seen that the animal has rather long, cylindrical tentacles
with black eyes at the base, a functional, small and short
foot, and patchy, brownish pigmentation.
Remarks: V. chondrocidaricola can be separated from
V. hawatiensis by its less projecting outer lip and less
inflated body whorl.
There are a few species of eulimids known that resem-
ble the two species of Vitreolina described here, but no
Indo-Pacific ones. The small size, pointed larval shell, and
low, rounded aperture make them easily distinguishable
from other eulimids. Another helpful detail is the suture,
which is distinctly curved just in front of, and after, the
incremental scars.
Pelseneeria Koehler & Vaney, 1908
Type species: Pelseneeria profunda Koehler & Vaney,
1908, subsequent designation Winckworth, 1932.
Remarks: The species of Pelseneeria are ectoparasites on
regular sea urchins. Most of them crawl around on the
test, presumably feeding on the epithelium or introducing
the proboscis into the tube feet to suck body fluid. One
previously known species (SCHEPMAN & NIERSTRASZ,
1909, as Stilifer sp.), from Aspidodiadema tonsum A. Agas-
siz, is known to be permanently attached, with its pro-
boscis introduced into a gonad of the host.
Pelseneeria sp.
In the collections of the Division of Mollusks, USNM,
there is a pair of specimens of Pelseneeria, from U.S. Fish-
eries Commission (USFC) “Albatross” Station 4044, 1902,
off Kawaihae Light, W coast of Hawaii, 356-520 m.
The shells have been completely dissolved by acidic al-
cohol, but the soft parts seem to be well preserved. Noth-
ing is mentioned about hosts. In AGASSIZ & CLARK’s (1908)
report on the Echinoidea from these dredgings, there is
mentioned only a single species of echinoid from the sta-
tion mentioned above, wiz. Stereocidaris grandis (Déder-
lein). MORTENSEN (1928:22-23) disagreed with this iden-
tification and regarded this specimen as a distinct species,
Stereocidaris hawanensis Mortensen, 1928. He also men-
tioned that the specimen in question had gastropod egg
capsules attached at the periproct. The specimen is still
in the collections of the Division of Echinoderms, USNM
27334. Examination of the specimen revealed 9 egg cap-
sules attached to the test, but no enlarged gonopores were
_ noticed, although the dorsal part of the test was cleaned
of spines. It can, therefore, be assumed that these two
specimens represent a second Hawaiian species of Pelse-
neeria, parasitic on Stereocidaris hawaziensis, in addition to
P. hawaviensis. We will, however, not name it here, be-
cause the absence of the shell would complicate future
identification.
Pelseneeria hawauensis
Waren, B. Burch & T. Burch, spec. nov.
(Figures 22, 25, 26)
Type material: Holotype USNM 111067 and 2 para-
types, USNM 792380.
Type locality: Attached by the proboscis (which is intro-
duced through the gonopore) on a specimen of Aspidodi-
A. Warén et al., 1984 Page 177
YF
22
20 21
Explanation of Figures 20 to 22
Figures 20 to 22. Apices. Figure 20. Trochostilifer hawatiensis. Figure 21. 7. entospinea. Figure 22. Pelseneeria hawatiensis.
Scale line = 0.25 mm.
Explanation of Figures 23 and 24
Figure 23. Aboral part of Aspidodiadema hawauense (USNM individual proboscides of the two pairs of parasitic snails. Scale
111067) with holes from proboscides of Pelseneeria hawatiensis. line = 2 mm.
a, anus of the sea urchin; 1,1 and 2,2 show the positions of the Figure 24. Pelseneeria hawaiiensis, holotype, 5.64 mm high.
Page 178
adema hawaiensis (Mortensen), USFC “Albatross” Sta-
tion 3865, Pailolo Channel, Hawaiian Islands, 500 m.
Material examined: The type material and: 2 specimens,
5.04 and 2.40 mm high, attached as above, on Aspidodi-
adema hawaiiensis, 11 Nov. 1979, 21°14.4’N, 157°56.6’W,
470 m, Mamala Bay, Oahu, Hawaiian Islands; (4 spec-
imens reported by AGassizZ & CLARK (1908), USFC “Al-
batross” Station 3839, off Lae-o, Ka Laau Light, Molo-
kai, Hawaiian Islands, 570-580 m and their host were
examined, but only fragments remained).
Description: Shell yellowish to brownish, rather thin and
fragile, rather broadly conical, with a blunt mucronate
larval shell. The larval shell (Figure 22) consists of about
2 slightly convex whorls and its axis forms a distinct angle
with that of the postlarval whorls. The holotype has 4.0
postlarval whorls, sculptured with faint incremental lines
and 3 irregularly placed and indistinct incremental scars.
The whorls are slightly convex and the suture is shallow
but distinct. The subsutural zone occupies about %, of the
height of the whorls. The periphery of the whorls is more
angulated than rounded, which gives the base of the shell
a rather flat appearance. The aperture is rather large and
evenly rounded in its lower part. The columella is thin
and the parietal wall is not covered by a callus.
Dimensions of holotype: Height of the shell 5.64 mm,
diameter 3.40 mm. Height of the aperture 2.47 mm.
Soft parts: Typical for Pelseneeria, but eyes are lacking.
The specimens did not leave the host when disturbed, but
had to be pulled off the host. The animal is unpigmented.
The proboscis is introduced through the gonopore which
becomes enlarged (cf. Figure 23). The part of the probos-
cis which is inside the gonad is greatly enlarged by being
filled with and inflated by the body-fluid of the parasite,
thereby probably functioning as an anchor and keeping
the snail in position on the host. The damage of the gono-
pore also indicates that the snail is permanently attached
to the same gonopore.
Remarks: SCHEPMAN & NIERSTRASZ (1909) never named
““Stilifer sp.” from Aspidodiadema tonsum because the shell
was broken. It is, therefore, not possible to say whether
their specimen belonged to a different species. The mode
of parasitism, being attached to the gonopores, distin-
guishes their species and P. hawazensis from all other
known species of Pelseneeria.
All specimens examined occurred in pairs, presumably
to ensure contact for copulation.
The present species was first reported on by AGASSIZ
The Veliger, Vol. 26, No. 3
& CLARK (1908) in their treatment of the echinoids taken
by the USFC in Hawaii. They had found four specimens
on one host (of which one pair can be seen on their plate
58, fig. 7), determined Aspidodiadema meyer A. Agassiz
& Clark (sic; the correct author is Déderlein). Mor-
TENSEN (1939), however, after having examined their
specimens regarded them as a distinct species and de-
scribed it as Aspidodiadema hawanensis Mortensen, 1939.
AGASSIZ & CLARK (1908) noticed that the genital plates
on which the snails were attached had more numerous
spines than the other genital plates. Their observation was
based on two parasitized genital plates; but, if this ten-
dency is persistent, the modification is certainly adaptive
for the parasite, giving better protection from grazing fish-
es.
ACKNOWLEDGMENTS
We want to direct our thanks to the Divisions of Mollusks
and Echinoderms, USNM, for examination of material of
hosts and parasites and for preparation of the SEM photos
of Trochostilifer. Warén’s work has been supported by
grants from the Swedish Natural Science Research Coun-
cil.
We also want to thank Mr. Keith Zeilinger, who col-
lected the specimens of Chondrocidaris.
LITERATURE CITED
Aoassiz, A. & L. H. CLARK. 1908. Hawaiian and other Pacific
Echini. The Salenidae, Arbacidae, Aspidodiametidae and
Diadematidae. Mem. Mus. Comp. Zool., Harv. 34:43-134.
Kay, E. A. 1979. Hawaiian marine shells. Reef and shore
fauna. 4. Bishop Museum Press, Honolulu. 652 pp.
MortTENSEN, T. 1928. A monograph of the Echinoidea. 1:1.
Cidaroidea. C. A. Reitzel, Copenhagen. 551 pp.
MortTENSEN, T. 1939. New Echinoidea (Aulodonta). Vidensk
Meddr. Dansk Naturh. Foren. 103:547-550.
SCHEPMAN, M. M. & H. F. Nierstrasz. 1909. Parasitische
prosobranchier der Sibogaexpedition. Siboga Expeditie 49(2):
1-27.
SCHOENBERG, D._ 1980. Living together—an old molluscan
custom. Hawaiian Shell News 28(11):3.
WareEN, A. 1980a. Revisions of the genera Thyca, Stilifer, Sca-
lenostoma, Mucronalia and Echineulima (Mollusca, Proso-
branchia, Eulimidae). Zool. Scr. 9:187-210.
Waren, A. 1980b. Descriptions of new taxa of Eulimidae
(Mollusca, Prosobranchia), with notes on some previously
described genera. Zool. Scr. 9:283-306.
WareENn, A. 1981. Revision of the genera Apicalia and Stilapex
and description of two new genera (Prosobranchia, Euli-
midae). Zool. Scr. 10:133-154.
Waren, A. In press. A generic revision of the family Euli-
midae. Journ. Moll. Stud., Suppl. 13.
The Veliger 26(3):179-182 (January 3, 1984)
THE VELIGER
© CMS, Inc., 1984
A New Species of [schnochiton
(Mollusca: Polyplacophora)
in the Gulf of California
ANTONIO J. FERREIRA!
Research Associate, Department of Invertebrate Zoology, California Academy of Sciences,
Golden Gate Park, San Francisco, California 94118
Abstract. A new species of chiton, /schnochiton carolianus Ferreira, spec. nov., is described from
San Carlos, Sonora (type locality) and Smith Island, Bahia de los Angeles, Gulf of California, Mexico,
dredged at depths of 61-91 m to 182 m. Specimens are very small (up to 8.5 mm long) resembling /.
tenuisculptus (Carpenter, 1864).
ALMOST SIMULTANEOUSLY, I was entrusted with two col-
lections of chitons from the Gulf of California, indepen-
dently obtained by Carol and Paul Skoglund, Phoenix,
Arizona, and Forrest and Leroy Poorman, Westminster,
California. As fortune would have it, both collections con-
tained specimens of a species which further study revealed
to be new to science.
Class Polyplacophora Gray, 1821
Order Neoloricata Bergenhayn, 1955
Suborder Ischnochitonina Bergenhayn, 1930
Family Ischnochitonidae Dall, 1889
Genus Ischnochiton Gray, 1847
Ischnochiton carolianus Ferreira, spec. nov.
(Figures 1 to 6)
Diagnosis: Very small (largest specimen, 8.5 mm long)
chitons, carinate, not beaked. Lateral areas well defined
with small, convex, round, granules in quincunx; central
areas pitted in quincunx; mucro anterior. Girdle with very
small, imbricated scales, with 10-12 riblets. Radula with
unicuspid major lateral teeth.
Type material: Holotype and 11 paratypes, dredged at
100 m, 5 km south of San Antonio Pt., San Carlos, Guay-
mas, Sonora, Mexico, /eg. Forrest and Leroy Poorman,
November 1980; and 3 paratypes, dredged at 61-91 m,
5 km south of Tetas de Cabras, San Carlos, Sonora, Mex-
' For reprints: 2060 Clarmar Way, San Jose, California 95128,
U.S.A.
ico, /eg. Carol and Paul Skoglund, November 1979. Ho-
lotype deposited at the California Academy of Sciences
(CAS 035074); paratypes, at the California Academy of
Sciences (CAS 035075), Los Angeles County Museum of
Natural History (LACM 2032), United States National
Museum of Natural History (USNM 749857), Academy
of Natural Sciences of Philadelphia (ANSP 357502) and
in the private collections of Carol and Paul Skoglund,
Forrest and Leroy H. Poorman, and Antonio J. Ferreira.
Other material: Smith Id. (north end), Bahia de los An-
geles, Gulf of California, Mexico, 3 specimens dredged at
182 m, leg. Carol and Paul Skoglund, May 1980.
Type locality: 5 km south of Punta San Antonio, San
Carlos, Sonora, Mexico (27°56'N; 111°906’W).
Description: Holotype (Figures 1, 2, 3)—dry specimen,
7.5 mm long, 4.5 mm wide, uniformly brown with some
irregular black smudges (? artifact) on valves and girdle
scales; valves moderately elevated and carinate; posterior
edge of intermediate valves, straight, not (or obsoletely)
beaked; lateral areas well defined, moderately elevated;
anterior valve, lateral areas of intermediate valves, and
postmucro area of posterior valve sculptured with incon-
spicuous, round, convex granules, about 80 um in diam-
eter, close together in quincunx; central areas minutely
punctated in quincunx; mucro anterior, inconspicuous;
postmucro, concave; girdle, 0.6 mm wide at valve iv, uni-
formly covered with very small, oval, imbricated scales;
gills unascertainable.
Paratypes—in several shades of brown (one mottled
with reddish hues), agreeing with holotype in all major
respects. Size range, including girdle, 8.5 x 5.4 mm to
Page 180 The Veliger, Vol. 26, No. 3
emp kienneiray 1984
)
)
a
=>
==
J
>
W
O
100 um
Figure 5
Ischnochiton carolianus Ferreira, spec. nov. Paratype (CAS
035075); dry specimen, 6.0 mm long, including girdle. Girdle
elements: A. scales of upper surface; B. scales of undersurface;
C. spicules of margin.
3.8 X 2.5 mm; body width/length, mean = 0.65 (SD =
O.35z IN = Wi),
Paratype (Figure 4), 6.0 x 4.0 mm, disarticulated: an-
terior valve, 1.0 mm long, 2.1 mm wide; posterior valve,
1.2 mm long, 2.2 mm wide, width of sutural laminae/
width of sinus = 0.4. Articulamentum white; sutural lam-
inae subrectangular, very short (0.2 mm long on valve
viii), almost continuous across a very shallow and poorly
defined sinus; insertion teeth sharp, small; slits 12-1-8
followed by slit-rays. Girdle’s upper surface covered with
strongly imbricated, oval scales (Figure 5A), up to 100
um long, with 10-12 riblets; undersurface with transpar-
ent, rectangular scales (Figure 5B), 50 x 20 um; marginal
fringe of inconspicuous spicules (Figure 5C), 60 x 30 um,
with oblique, screw-like striations. Radula, 2.0 mm long,
comprising 24 rows of mature teeth; median tooth about
120 um long, edges slightly incurved, 40 wm wide at an-
terior blade, 30 wm at waist; first lateral teeth, 50 um
long, with small knob at antero-outer corner (Figure 6A);
major lateral teeth with unicuspid head (Figure 6B); outer
marginal teeth 65 wm long, 45 wm wide.
Distribution: /schnochiton carolianus is known only from
the type locality, San Carlos, Sonora, Mexico, and Smith
Id., Bahia de los Angeles, Gulf of California, Mexico, at
depths of 61-91 m to 182 m.
Remarks: /schnochiton carolianus resembles J. tenuisculp-
tus (Carpenter, 1864), a species occurring from Panama
to Peru, in color, shape of body, and the simplicity of
Page 181
l =|
100 yum
Figure 6
Ischnochiton carolianus Ferreira, spec. nov. Paratype (CAS
035075); dry specimen, 6.0 mm long, including girdle. Radula:
A. median and first lateral teeth; B. head of second (major)
lateral tooth.
tegmental features. The two species seem to differ in size
(largest specimen examined of carolianus, 8.5 mm long;
of tenuisculptus, 15.8 mm long), and are quite distinct in
the (1) tegmental granules of lateral areas and end valves
(regular in size and height in carolianus; larger and higher
round granules, standing out, randomly, amidst smaller
and lower ones in tenwisculptus); (2) mucro (definitely
anterior in carolianus; central or only slightly anterior in
tenuisculptus); (3) girdle scales (up to 100 um long in
carolianus; up to 180 um long in tenuisculptus); and (4)
radula’s major lateral teeth (unicuspid in carolianus; bi-
cuspid in tenursculptus).
The species is here called carolianus after Carol Skog-
lund, Phoenix, Arizona, who, together with her husband
Paul E. Skoglund, first collected and made available spec-
imens for study.
ACKNOWLEDGMENTS
Appreciation is here expressed to Carol and Paul E. Skog-
lund and to Forrest L. and Leroy H. Poorman, who pro-
vided the material for study; and to Dr. Barry Roth, Cal-
ifornia Academy of Sciences, who critically reviewed the
manuscript.
LITERATURE CITED
BERGENHAYN, J. R. M. 1930. Kurze bemerkungen zur kennt-
nis der schalenstruktur und systematik der Loricaten. Kungl.
Explanation of Figures 1 to 4
Figure 1. Ischnochiton carolianus Ferreira, spec. nov. Holotype
(CAS 035074); dry specimen, 7.5 mm long, including girdle.
Figure 2. Same as in Figure 1. Side view.
Figure 3. Same as in Figure 1. Close-up of lateral and pleural
areas.
Figure 4. [schnochiton carolianus Ferreira, spec. nov. Paratype
(CAS 035075); dry specimen, 6.0 mm long, including girdle.
Tegmental side of valves i, vi, and viii.
Page 182
Svenska Vetensk. Handl. (3) 9(3):3-54, 5 text figs., 10 plts.
Uppsala. (November 11).
BERGENHAYN, J. R. M. 1955. Die fossilen schwedischen Lori-
caten nebst einer vorlaufigen. Revision des systems der gan-
zen Klasse Loricata. Lunds Universitets Arsskrift. N.F. Avd.
2, vol. 5, no. 8. Kungl. Fysiogr. Sallsk. Handl. N.F. 66(8):
3-42, 2 tbls. (August 3).
CARPENTER, P. P. 1864. Review of Prof. C. B. Adam’s “‘Cat-
alogue of the Shells of Panama,” from the type specimens.
Proc. Zool. Soc. London (for 1863) (3):339-369.
The Veliger, Vol. 26, No. 3
Da.LL, W. H. 1889. Preliminary catalogue of the shell-bearing
marine mollusks and brachiopods of the southeastern Coast
of the United States, with illustrations of many of the species.
Bull. U.S. Nat. Mus. 37:3-221; 74 plts. (May 27, 1889).
Gray, J. E. 1821. A natural arrangement of Mollusca, ac-
cording to their internal structure, London Medic. Repos.
15:229-239.
Gray, J. E. 1847. Additional observations on Chitones. Proc.
Zool. Soc. London 15(178):126-127 (? 30 Noy. 1847).
The Veliger 26(3):183-187 (January 3, 1984)
Ara, Wisin
© CMS, Inc., 1984
Records of Cuthona pustulata (Alder & Hancock, 1854)
from the Canadian Pacific
TERRENCE M. GOSLINER'
Division of Mollusks, National Museum of Natural History,
Smithsonian Institution, Washington, D.C. 20560
SANDRA V. MILLEN
Department of Zoology, University of British Columbia,
Vancouver, British Columbia, Canada V6T-2A9
Abstract. A tergipedid nudibranch found in the shallow subtidal waters of British Columbia, Can-
ada, differs from all known sympatric species. Specimens closely resemble the descriptions of Cuthona
pustulata (Alder & Hancock, 1854) previously known only from the northeastern Atlantic. The mor-
phology of this species in both the northeastern Pacific and northeastern Atlantic is compared. Closely
related and sympatric species are discussed.
INTRODUCTION
A TERGIPEDID nudibranch first collected at Saltspring Is-
land, Strait of Georgia, British Columbia, Canada, in May
1977, differed substantially from the four known sympat-
ric tergipedid species (Catriona columbiana [O’ Donoghue,
1922], Cuthona albocrusta {MacFarland, 1966], C. concin-
na [Alder & Hancock, 1843] and C. divae [Marcus, 1961]).
This species, identified as Cuthona pustulata (Alder &
Hancock, 1854) has been previously recorded from the
northeastern Atlantic. Its presence in the northeastern Pa-
cific represents a significant addition to its known range.
The genus Cuthona has been enlarged considerably,
particularly in recent years. Trinchesia, Xenocratena, Ca-
triona, Njurja, Narraeolidia, Toorna, and Selva are pres-
ently considered junior synonyms by MILLER (1977). The
inclusion of the genus Catriona, however, has been dis-
puted by GOSLINER & GRIFFITHS (1981). WILLIAMS &
GOSLINER (1979) added Precuthona, as the type species
Precuthona peachi (Alder & Hancock, 1848) appears to
be a junior synonym of the type species of Cuthona, Cu-
thona nana (Alder & Hancock, 1842). GOSLINER (1981)
also included Subcuthona, making a total of over 80 species
‘Permanent address: Department of Invertebrate Zoology,
California Academy of Sciences, San Francisco, California.
in this genus. Cuthona species are listed primarily in
Marcus (1958), SCHMEKEL (1968), BURN (1973), and
WILLIAMS & GOSLINER (1979). BROWN (1980) rede-
scribed British species including the type species Cuthona
nana.
MATERIAL
On May 1, 1977, the first two specimens of Cuthona pus-
tulata were collected by S. Millen, 15 m below Canadian
datum at Musgrave Landing, Saltspring Island, British
Columbia (latitude 48°48’N; longitude 123°32’W). On
April 18, 1980, an additional eight specimens were col-
lected from Halecium sp. by R. Long diving at 12 m in
the same area.
At Porlier Pass, Galiano Island, British Columbia (lat-
itude 49°01'N; longitude 123°36’W) on April 29, 1979,
two specimens were collected by S. Millen on Halecium
sp. at a depth of 10 m. A dive at this site by S. Millen on
May 2, 1982, yielded 33 specimens and spawn on Hale-
cium sp. at depths of 14-18 m. Seven voucher specimens
have been deposited in the British Columbia Provincial
Museum, BCPM 983.26.1, and six voucher specimens in
the California Academy of Sciences, CASIZ 031673.
DESCRIPTION
The body is slender (Figure 1) and up to 20 mm in length.
Body color is translucent white with opaque white ovo-
Page 184
ihe Veliger) Vola ZoNows
Figure 1
Cuthona pustulata, 16 mm in length. Drawn from a color transparency taken by Ron Long.
testis and brown jaws visible through the skin. The oral
tentacles are cylindrical with blunt tips. They arise from
the antero-lateral corners of the head and are flecked on
the dorsal surface with opaque white spots. The rhino-
phores are smooth and slightly longer than the oral ten-
tacles. They arise close to each other. Fine, opaque white
spots decorate the rhinophores except near their bases.
The head is globular with a T-shaped mouth opening.
The cerata are elongate and cylindrical, with rounded
tips containing small, white cnidosacs. The liver divertic-
20 pm
Figure 2
Radular tooth drawn from a SEM micrograph.
ula are dark reddish brown and granular. The ceratal
sheath is transparent. Above the cnidosacs, the ceratal tips
are clear. Each bears a faint, opaque white subapical band.
There are small opaque white flecks on the distal halves
of the cerata, and two or three large white spots on the
proximal halves. The cerata are arranged in 8 to 14 rows.
An example of the ceratal arrangement of a typical 16-
mm specimen (live length) is 2,4,6,7,8; 6,6,5,4,4,3 on the
right and 3,4,6,5,7; 6,6,4,4,3,2 on the left (using the count-
ing method of EDMUNDs, 1970). The pre-cardiac rows
are opposite; the post-cardiac rows are slightly anterior
on the left side. The anus is posterior in the inter-hepatic
space, just below the cardiac hump, with the renal pore
directly ahead of it. The gonopore is below the second or
third ceratal row of the right anterior liver branch.
——
1mm
Figure 3
Jaw with a single row of denticles on the masticatory margin.
T. M. Gosliner & S. V. Millen, 1984
Figure 4
A. Cuthona pustulata reproductive system from a camera lucida
drawing. Key: a, female aperture; amp, ampulla; gl, penial gland;
mem, membrane gland; mu, mucous gland; ovi, oviduct; ovo,
ovotestis; p, penis in sac; pd, preampullary duct; pr, prostate; rs,
receptaculum seminis; sp, spermoviduct; vd, vas deferens. B.
Penial tip showing stylet and vas deferens.
The foot is rounded anteriorly with a thickened anterior
margin and a small flange. The long, pointed tail has an
irregular line of opaque white spots.
The uniseriate radula contains 12 to 26 teeth. The cen-
tral cusp is slightly shorter or equal in length to the first
of the five to six laterals on each side (Figure 2). There
is sometimes a small intermediate denticle on each side of
the central cusp. The thin, triangular jaws (Figure 3) have
a well developed masticatory margin with approximately
16 fine denticulations.
In the reproductive system (Figure 4) the ovotestis is
connected by the preampullary duct to a small U-shaped
ampulla. The postampullary duct branches to form an
oviduct entering the female gland mass and a vas deferens
enlarged into a prostatic portion. The more distal, non-
prostatic portion of the vas deferens enters the penial sac
at the junction of the large, unstalked, penial gland. The
penis has a short, conical, 44-125 um long, stylet (Figure
Page 185
Figure 5
A. Egg mass of Cuthona pustulata laid on the hydroid Halecium
sp. B. Close-up of the egg mass showing the single eggs and
large capsules.
4B). There is a round, stalked receptaculum seminis near
the separate, female aperture.
Spawning was observed in two different years in early
May. The eggs (Figure 5) are laid on the shafts of Hale-
cium sp., towards the center of these hydroid colonies, in
concealed locations. The spawn ribbon, a white, convo-
luted coil attached by a small membrane, forms a sausage-
shaped mass. The oval egg capsules are much larger than
the eggs (Figure 5B). One egg 120 um in diameter is
typical for each capsule, but occasionally there are two or
three.
After 18 to 19 days at 10°C, the eggs hatched into
planktotrophic veligers with Type 2 shells of THOMPSON
(1961). The veligers developed eyes after three days and
appeared competent by two weeks. Shortly after hatching
the digestive gland turned green, an indication that the
larvae were feeding. Metamorphosis did not take place
and the veligers died after three weeks.
HABITAT
Animals were found subtidally on the hydroid Halecium
sp. on rocky bottoms, 10 to 18 m below Canadian datum,
in April or early May. In two different years the collection
localities were rechecked unsuccessfully in June. Appar-
ently the period of peak abundance is short.
DISCUSSION
Most Cuthona species vary considerably in coloration but
have colors other than white on their notum, cerata, oral
Page 186 The Veliger, Vol. 26, No. 3
Table 1
Cuthona pustulata from Britain and the northeastern Pacific.
Locality Britain (from BRown, 1980) Northeastern Pacific
Max. live length 13 mm 20 mm
Preserved length 8 & 11 mm Awan 7/ inven 1 seat
No. ceratal rows 12 8 11 14
No. precardiac rows 6 3} 5 6
Max. no. cerata 126 52 105 230
Max. no. cerata/row 8 5 7 5
Color:
Ceratal epidermis
Ceratal cores
large white spots
It. brown/pink/yellow
Tentacles white patches
Rhinophores white patches
No. radular teeth 15-24
No. tooth denticles
Jaw margin
Penial gland
Penial armature
Vas deferens
Seminal receptacle
Spawn mass
finely denticulated
base of vas deferens
conical stylet
prostatic portion
near female opening
white, small coils
No. eggs approx. 700/spawn mass
Egg size 180 pm
Larvae ? non-pelagic
tentacles, or rhinophores. The large, distinctive, white spots
on the cerata of our specimens, and absence of any other
colors, were characteristics shared only by C. fulgens
(MacFarland, 1966), C. perca (Marcus, 1958), and C.
pustulata (Alder & Hancock, 1854).
Cuthona fulgens differs from our specimens in that the
hepatic lobes of the cerata have a lemon-yellow band at
their bases and below the cnidosacs. In addition, the rad-
ula of C. fulgens has a much larger number of teeth (59
compared to a maximum of 26 in our specimens), and its
receptaculum seminis is located on a longer stalk, more
distally positioned with respect to the female aperture.
Cuthona perca sometimes has olive-green flecks and a
light orange head. When these are absent it nevertheless
differs from our specimens in having olive-green to
brownish digestive gland tissue in the cerata and notum.
The radula has more teeth (35) with more denticles (up
to 11 on each side of the central cusp). The rhinophores
and oral tentacles of C. perca are shorter. It has a larger,
more distinct inter-hepatic space and a longer tail. The
spawn of C. perca is saccate, not coiled like that of our
specimens. Lastly, C. perca has been observed to feed on
anemones, not hydroids (GOSLINER, 1980).
Cuthona pustulata has been redescribed by BROWN
(1980). Only minor differences were found between his
material and ours (Table 1). The ceratal core variations
found in the Pacific animals did not exhibit the range
observed in Britain. Cuthona pustulata is known from Brit-
tany, France to Iceland (BROWN, 1980). The addition of
a locality in the northeastern Pacific suggests that it is an
4-7/side; central shorter
large white spots
reddish brown
white patches
white patches
12-26
5-9/side; central shorter or equal
13-16 fine denticles
base of vas deferens
conical stylet
prostatic portion
near female opening
white, one convoluted coil
approx. 450/spawn mass
120 pm
planktotrophic; shell Type 2
amphi-boreal species which can be expected to range fur-
ther northward in the Pacific.
Cuthona pustulata can be distinguished from sympatric
tergipedid species in the northeastern Pacific. Cuthona al-
bocrusta has short, inflated cerata with pointed tips rather
than elongate, cylindrical ones; Catriona columbiana has
orange rhinophore bands and white ceratal lines; Cuthona
concinna has purple or brown hepatic lobes in the cerata,
and C. divae has a greater number of cerata which extend
anterior to the rhinophores. None of these sympatric species
have large, opaque white spots on the cerata. There are
significant internal differences as well. Cuthona concinna
and C. divae lack a penial stylet. Cuthona albocrusta has
more radular teeth (56-70) as does Catriona columbiana,
which has a strongly tapered radula with a pre-radular
tooth and upwards of 100 teeth. None of these species is
found living on hydroids belonging to the genus Halecium.
ACKNOWLEDGMENTS
We would like to thank Ron Long for photography and
assisting in the collection of specimens and Sven Donald-
son for his comments on the manuscript.
LITERATURE CITED
Brown, G. H. 1980. The British species of the aeolidacean
family Tergipedidae (Gastropoda: Opisthobranchia) with a
discussion of the genera. Zool. J. Linn. Soc. 69:225-255
(July, 1980).
Burn, R. 1973. Opisthobranch molluscs from the Australian
T. M. Gosliner & S. V. Millen, 1984
Page 187
Sub-Antarctic territories of Macquarie and Heard Islands.
Proc. Roy. Soc. Victoria 86:39-46 (5 October, 1973).
EpMuNnbs, M. 1970. Opisthobranch Mollusca from Tanzania.
II Eolidacea (Cuthonidae, Piseinotecidae and Facelinidae).
Proc. Malacol. Soc. Lond. 39:15-57.
GosLINER, T. M. 1980. The systematics of the Aeolidacea
(Nudibranchia: Mollusca) of the Hawaiian Islands, with
descriptions of two new species. Pac. Sci. 33:37-77.
GosLINER, T. M. 1981. A new species of tergipedid nudi-
branch from the coast of California. J. Moll. Stud. 47:200-
205.
GosLiner, T. M. & R. J. GRIFFITHS. 1981. Descriptions and
revision of some South African aeolidacean Nudibranchia
(Mollusca, Gastropoda). Ann. S. Afr. Mus. 84:105-150
(July, 1981).
Marcus, E. 1958. Western Atlantic opisthobranchiate gastro-
pods. Amer. Mus. Novitates No. 1906:1-82 (13 August,
1958).
MILLER, M. C. 1977. Aeolid nudibranchs (Gastropoda Opis-
thobranchia) of the family Tergipedidae from New Zealand
waters. Zool. J. Linn. Soc. 60:197-222 (April, 1977).
SCHMEKEL, L. 1968. Vier neue Cuthonidae aus dem Mittel-
meer (Gastropoda Nudibranchia): 77inchesia albopunctata n.
sp., Trinchesia minwstriata n. sp., Trinchesia ilionae n. sp.,
und Catriona maua Marcus and Marcus, 1960. Pubbl. Staz.
Zool. Napoli 36:437-457.
THompson, T. E. 1961. The importance of the larval shell in
the classification of the Sacoglossa and the Acoela (Gastrop-
oda Opisthobranchia). Proc. Malacol. Soc. London 34:233-
238.
WILLIAMS, G. C. & T. M. GosLINER. 1979. Two new species
of nudibranchiate molluscs from the west coast of North
America with a revision of the family Cuthonidae. Zool. J.
Linn. Soc. 67:203-223 (November, 1979).
The Veliger 26(3):188-198 (January 3, 1984)
THE VELIGER
© CMS, Inc., 1984
The Ecology of Parvilucina tenuisculpta
(Carpenter, 1864) (Bivalvia: Lucinidae) on the
Southern California Borderland
GILBERT F. JONES anp BRUCE E. THOMPSON!
Department of Biological Sciences, University of Southern California,
Los Angeles, California 90089
Abstract. The pelecypod Parvilucina tenuisculpta (Carpenter, 1864) is a widely distributed member
of the benthos of the southern California borderland where it is a prominent faunal element of every
major habitat except the deep basins. In this fairly wide range of environments it lives with a large
number of other taxa which may differ markedly from one location to another. The population densities
of Parvilucina were highest in two very dissimilar environments—the insular shelf of the northern
Channel Islands and the central part of the mainland shelf (Santa Monica Bay and San Pedro Bay).
The insular shelf is primarily a non-depositional environment where relatively strong currents result
in the development of coarse sediments rich in biogenic calcium carbonate components. The area is
influenced by persistent upwelling. By contrast, the parts of the mainland shelf where population
densities of Parvilucina were highest are in equilibrium environments highly influenced by the release
of sewage wastewaters. Organic enrichment, in one case upwelling and the other sewage wastewaters,
may be the factor responsible for the areas of high population densities.
INTRODUCTION
THE SEA FLOOR OF southern California and northern Baja
California is much more complex than continental shelves
in most other areas of the world. The region is complex
and different enough to have been designated by a special
term, ‘“‘the continental borderland” (SHEPARD & EMERY,
1941; UcHuPI & EMERy, 1963). The part of the border-
land that forms the Southern California Bight includes
islands, banks, ridges, basins, and troughs. The bathym-
etry spans the range from the sublittoral zone to the bathyal
depths (EMERY, 1960). Numerous submarine canyons
transect the mainland and island shelves, descending to-
ward and into the basins. Imposed upon this structural
variety is a highly diverse substrate pattern. Consequent-
ly, the sea floor of the Bight consists of a very complex
set of benthic habitats, and the diversity of the benthic
macrofauna reflects this complex habitat (EMERY, 1960;
FAUCHALD & JONES, 1978, 1979a, b; HARTMAN, 1955,
‘Current address: Southern California Coastal Water Re-
search Project, 646 W. Pacific Coast Highway, Long Beach,
California 90806.
1956, 1963, 1966; HARTMAN & BARNARD, 1958, 1960;
JONES, 1969).
The pelecypod Parvilucina tenuisculpta (Carpenter,
1864) (=Lucina tenuisculpta) (Figure 1) is an important
member of the benthos of the southern California conti-
nental borderland. It has been collected in most of the
major quantitative studies of the benthic macrofauna of
the borderland. The purpose of this paper is to review
these findings and to document the distribution, abun-
dance, spatial and temporal variation, feeding and faunal
associates of P. tenuisculpta in the region.
In an extensive survey of the benthos of the San Pedro
Basin, HARTMAN (1955, 1966) recorded the biological
components of 267 samples. WILSON (1956) reported Par-
vilucina in 18 of Hartman’s samples. The population den-
sities varied from 4 to 72 per m? (mean = 24.4/m?) in
depths ranging from 14.6 to 702.5 m (mean = 178.7 m).
In a paper on the dominant benthic molluscan faunas of
the San Pedro Basin based on Wilson’s data, BANDY (1958)
included Parvilucina tenuisculpta as one of the elements of
his Fauna 2 (dominant pelecypod faunas; the other mem-
bers of this faunal group are Nuculana taphria, Solamen
columbianum, Solemya panamensis, Solen rosaceus and Thy-
asira barbarensis). Parvilucina was reported only once (Sta-
G. F. Jones & B. E. ‘Thompson, 1984
Page 189
tion 3492, 3 specimens in 47.3 m) by HARTMAN (1956)
in her study of the benthic macrofauna of Santa Monica
Bay, but most of the molluscan specimens collected in this
survey were not identified to species.
From 1956 to 1961, the California Water Quality Con-
trol Board supported an extensive investigation of the
oceanography, geology, and marine biology of the main-
land shelf of southern California. During the study the
benthic macrofauna was sampled at 456 locations (AHF:
USC, 1965). Parvilucina tenuisculpta was collected at 78
(17%) of the sampling locations of this study with popu-
lation densities ranging from 4 to 68 per m? (mean =
12.0/m*) in water depths ranging from 13 to 253 m
(mean = 66.5 m). It was absent from the 121 Van Veen
grab samples collected from the shallower portion (2.4 to
10.1 m) of the shelf.
In her study of the benthic macrofauna of the subma-
rine canyons of the borderland HARTMAN (1963) reported
Parvilucina from Hueneme and Redondo submarine can-
yons. In their study of the benthos of the basins of the
borderland HARTMAN & BARNARD (1958, 1960) did not
record Parvilucina as a faunal element of any basin.
Working with a group of Allan Hancock Foundation
scientists, FAUCHALD (1971) studied the impact of the
Santa Barbara oil spill (1969) on the biota of the Santa
Barbara shelf. Parvilucina tenuisculpta (reported as Pha-
coides tenuisculpta) was collected in more than 10% of the
85 samples in this study.
In a survey of the mainland shelf conducted by the
Southern California Coastal Water Research Project
(SCCWRP) in 1977, benthic samples were collected at
intervals of approximately 10 km at a depth of 60 m along
the entire length of the mainland shelf from Point Con-
ception to the US-Mexican border. Very high densities of
Parvilucina, approaching 10,000/m/?, were encountered off
the Palos Verdes Peninsula and in Santa Monica Bay;
densities along the 60-m transect north and south of these
two areas were very much lower by comparison (WORD
& MEARNS, 1978, fig. 4).
The present paper is based on data gathered during
two major studies of the benthos of southern California
funded by the Bureau of Land Management, the Baseline
Study (1975-1976) and the Benchmark Study (1976-
1977). These two studies, together, are the largest inves-
tigations of this kind ever made in this marine region
(FAUCHALD & JONES, 1978, 1979a, b).
The benthic macrofauna was sampled at over 700 lo-
cations during the Baseline Study; 546 of these sampling
locations were grouped in 11 regular grids termed High
Density Sampling Areas (HDSAs); within these grids
sampling stations were arranged on 1.7-km (1-mile) cen-
ters. These grids varied in size from 16 to over 100 sam-
pling locations. Four of these HDSAs were on the main-
land shelf and its slopes; one was on the Santa Catalina
Ridge; two were on the insular shelf of the Channel Is-
lands; and four were on the Santa Rosa-Cortes Ridge.
ITTITINITIT LE
Figure 1
Parvilucina tenuisculpta (Carpenter, 1864). Larger specimens are
from an outfall area; smaller specimens from near Point Con-
ception. Scale in millimeters.
Another 227 sampling stations were located outside the
HDSAs.
During the Benchmark Study, replicate sampling was
conducted at 21 sampling stations in six areas of the bor-
derland: off Coal Oil Point and the slope of the Santa
Barbara Basin (3 stations); off San Pedro, on the slope of
San Pedro Basin and within the basin (6 stations); south
of San Miguel Island (2 stations); south of Santa Rosa
Island (1 station); on the northern portion of the Santa
Rosa-Cortes Ridge south of Santa Rosa Island, the slope
of Santa Cruz Basin and within the basin (3 stations);
and on the southern portion of the Santa Rosa-Cortes
Ridge, including Tanner Bank, the slope of San Nicolas
Basin and within the basin (6 stations). Sampling was
conducted twice during the year, once in the period of low
water temperature (early spring) and once in the period
of high water temperature (early fall). Eight replicate
samples were collected at each station during each sam-
pling period.
METHODS
In both the Baseline and Benchmark studies, a navigational
system was used that could guarantee an accuracy of +30.5
m.
Samples were collected by a modified 1/16 m*? USNEL-
Reineck spade (or box) corer (HESSLER & JUMARS, 1974).
A subsample of each core was collected for sedimentary
analysis. Benthic samples were screened through 1.0 mm
and 0.5 mm stainless steel screens using the overflow-
barrel method. The benthic macrofaunal invertebrates were
narcotized for 20 min in 6% magnesium chloride in sea-
Page 190
The Veliger, Vol. 26, No. 3
120° 119
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SAN MIGUEL
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SOUTHERN CALIFORNIA
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DIEGO
Figure 2
Chart of southern California borderland showing locations where Parvilucina tenuisculpta was collected. Circle-size
reflects population density; see legend.
water prior to killing and fixation; specimens were killed
and fixed in 10% buffered seawater formalin; after 36 h
samples were transferred to 70% ethanol for preservation.
The rapid identification procedure was used to analyze
the benthic samples (FAUCHALD & JONES, 1978). Some
taxa were identified to the specific level, whereas others
were identified only to the familial or generic level under
the limitations of this method. All taxa were identified to
species (where possible) for 165 of the 712 samples col-
lected during the Baseline Study and for all of the 318
samples collected during the Benchmark study.
The diet and mineral particle-size range used by Par-
vilucina tenuisculpta in the major benthic habitats of
the southern California borderland were analyzed
(THOMPSON, 1982). The gut contents of 20 specimens from
all habitats, offshore and mainland shelves, near and away
from sewage outfalls, winter and summer, were examined
microscopically (10-100) and the material categorized
into five food groups: (1) detrital aggregates, (2) single
mineral particles, (3) particulate organic material, (4) an-
imal remains, and (5) Foraminifera. The proportion of
each of the food groups in total sample volume was esti-
mated visually to the nearest 10%. The sizes of mineral
particles ingested were measured to the nearest 10 wm
using a light microscope (1000). Because of the small
sample size obtained from each specimen, the gut contents
of five specimens from Stations 805 and 806 were pooled.
A total of 150 particles from 15 random fields were mea-
sured.
The spatial dispersion of P. tenuisculpta at two different
sampling scales was determined using an Index of Dis-
persion (MorisiTA, 1959).
Determination of the organisms associated with Parvi-
lucina was based on the faunal composition of represen-
tative sample-sets each consisting of 10 samples.
Sedimentary analyses were made by geologists at Cal-
POPULATION DENSITY (NO./M’
G. F. Jones & B. E. Thompson, 1984
2000
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500
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e
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400 e
e e e
300 O 0
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eee
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e e
200 * ~
e
eo e e e
8 ° e
ee eee ee x
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Page 191
DEPTH
Figure 3
Depth distribution of Parvilucina tenuisculpta on the southern California borderland. The symbol x indicates the
position of the mean depth and the mean density.
ifornia State University, Northridge (Baseline Study) and
University of California, Los Angeles (Benchmark Study).
RESULTS
Geographic Distribution
Parvilucina tenuisculpta is widely distributed through-
out the southern California borderland (Figure 2). KEEN
(1937) records the distribution of Parvilucina tenuisculpta
as from 32°N to 60°N latitude (midpoint of range, 46°N)
along the west North American coast, or approximately
from Ensenada, Baja California to Cook Inlet, Alaska. It
is a prominent faunal element of every major habitat type
in the borderland except the deep basins. On the mainland
shelf it occurs from Point Conception to the US-Mexican
Border. It is an important element of the biota of the
insular shelf of the Channel Islands and occurs on the
Santa Rosa-Cortes Ridge including Tanner and Cortes
Banks. It also occurs on the Santa Catalina Ridge north
of Santa Catalina Island.
Parvilucina was collected at 226 (31.7%) of the 712
stations during the Baseline Study. Population densities
ranged from 16 to 2560 individuals per m? (mean = 139.1/
m’). Densities were highest in two very dissimilar envi-
ronments—the insular shelf of the Channel Islands (the
San Miguel Island HDSA and the Santa Rosa HDSA)
and the central part of the mainland shelf in Santa Mon-
ica Bay and San Pedro Bay (including the Huntington
Beach HDSA).
The insular shelf of the Channel Islands is primarily a
nondepositional environment. Relatively strong currents
result in winnowing of finer detrital sediments and the
development of ripple marks. Sediments are frequently
coarse and relatively high in calcium carbonate content,
and the sediment patterns of the region tend to be com-
plex. Evidence of bioturbation is minimal. The area may
be influenced by the persistent upwelling centers of the
Point Conception area (R. C. Dugdale, personal com-
munication) and the upwelling resulting from the entrain-
ment of deeper, subsurface water by the California Cur-
rent across the Santa Rosa-Cortes Ridge (EMERY, 1960).
Page 192
Table 1
A comparison of the habitat, depth and sediment charac-
teristics of Parvilucina tenuisculpta on the Insular Shelves
and the Mainland Shelf. Mean, range, and number of
stations sampled are given for each variable.
Environmental
variable Insular shelf Mainland shelf
Number/m? 157.0 187.5
16-1872 16-2560
(85 stations) (85 stations)
Depth (m) 124.0 90.7
26-416 13-332
(85 stations) (85 stations)
Mean phi 3),5) 4.4
1.4-4.4 1.0-6.2
(72 stations) (67 stations)
Percent gravel 2.0 1.0
0.0-28.0 0.0-57.0
(72 stations) (67 stations)
Percent sand WO 49.8
54.0-98.0 3.0-99.0
(72 stations) (67 stations)
Percent silt 14.5 42.1
1.0-38.0 0.0-84.0
(72 stations) (67 stations)
Percent clay 4.0 Holl
0.0-11.0 2.0-23.0
(72 stations) (67 stations)
Percent CaCO, Dale 4.5
3.1-54.8 0.2-53.5
(70 stations)
(53 stations)
Parvilucina was collected at 34 (72%) of the 47 stations
comprising the San Miguel Island HDSA; population
densities ranged from 16 to 544 individuals per m? (mean
= 124.9/m?). It was present in 52 (51%) of the 102 sta-
tions forming the Santa Rosa Island HDSA; in this sam-
pling grid, population densities ranged from 16 to 1872
individuals per m* (mean = 161.8/m7?).
By contrast, the areas on the mainland shelf where den-
sities of Parvilucina are high are equilibrium environ-
ments modified by man’s activities, particularly the release
of domestic and industrial wastewater into the marine
environment. The combined discharge levels are in excess
of one billion gallons of effluent per day (SCHAFER, 1980).
Except for areas of rock and relic sediments, sediments in
this area are finer, much lower in calcium carbonate and
higher in total organic content than on the insular shelf.
Neither strong currents nor major upwelling are major
factors in the area.
On the mainland shelf at 34 stations in Santa Monica
Bay and San Pedro Bay, population densities ranged from
16 to 2560 individuals per m? (mean = 247.8/m?). Fur-
ther south, in the Huntington Beach HDSA, Parvilucina
occurred at 19 (73.1%) of the 26 stations comprising the
grid, with population densities ranging from 32 to 380
individuals per m? (mean = 199.0/m7).
The Veliger, Vol. 26, No. 3
High population densities also were recorded on the
mainland shelf in one other area, off Point Conception.
At Station 830 the density was 1568 per m? and at Station
835 the density was 2192 per m’.
Distribution by Depth
The depth distribution of Parvilucina tenuisculpta re-
flects the fact that this species primarily inhabits the to-
pographic highs—shelves, ridges, and banks—of the bor-
derland. The 226 sampling locations where it was collected
ranged in depth from 13 to 433 m (mean = 126.6 m); the
sampling locations on the insular shelf of the Channel
Islands were somewhat deeper (range, 26-416 m; mean =
124.0 m) than those on the mainland shelf range, 13-322
m; mean = 90.7).
The depth distribution of this species on the southern
California borderland is illustrated in Figure 3. Over half
(54.4%) of the stations where Parvilucina was collected
were in depths of 100 m or less, where the mean density
was 177.7/m*. Over 90% of all the samples containing
Parvilucina were collected at depths of 300 m or less.
The 18 samples collected by HARTMAN (1955, 1966)
and analyzed by WILSON (1956) had a considerably great-
er depth range than the samples collected during the BLM
Projects; their San Pedro Bay samples were collected in
depths ranging from 14.6 to 702.5 m (mean = 178.8). By
contrast, the 78 samples collected from the mainland shelf
during the Water Quality Control Project (AHF:USC,
1956) had a more limited range (13 to 253 m; mean =
66.5 m). Combining the data from these two surveys with
that of the BLM study the overall range of this species in
the borderland is from 13 to 702 m (mean = 114.7).
Distribution in Relation to Sediments
Data are available on the sedimentary characteristics of
the substrate at most of the sampling locations (186 and
226) where Parvilucina tenuisculpta was collected. A com-
parison of the habitat of Parvzlucina on the Channel Island
shelf and the mainland shelf is presented in Table 1. Sed-
iments, in general, are coarser on the insular shelf than
on the mainland shelf (average mean phi of 3.3 compared
to 4.4). An important difference between these two envi-
ronments is that the calcium carbonate content of the sed-
iments is much higher on the island shelf than on the
mainland shelf (mean of 21.7% compared to 4.5%). This
illustrates the fact that in the non-depositional environ-
ment of the insular shelves, biogenic contributions of cal-
cium carbonate materials are a much more important sed-
imentological component than in the equilibrium
environment of the mainland shelf.
Spatial and Temporal Variation
Limited information was available on the temporal
variation of Parvilucina tenuisculpta populations. Only a
single-year sequence (winter-summer) was analyzed and
G. F. Jones & B. E. Thompson, 1984
Rage iOS
Table 2
Average densities and indices of dispersion (I;) and seasonal comparisons for Parvilucina tenuisculpta from benchmark
sites. Samples were subdivided during sample processing into two sample fractions: the 1.0-mm fraction, all specimens
collected on a 1.0-mm mesh screen and the 0.5-mm fraction, all specimens collected on a 0.5-mm screen. Density data
are presented for each fraction.
: ra Mann-
Sample MunteR piesele fees Gaetan a ae aimee Whitney
frac- Mean Mean (Uy
Sta- Depth tion density density winter us
tion (m) (mm) (No./m?) I, x? N (No./m7?) I, x? N summer
Mainland shelf
819 32 1.0 10.1 3.20 15.8 8 2.0 0) 7.0 8 50
0.5 8.0 2 136.0 D,
801 68 1.0 Des 2.33 20.3* 8 12.0 1.60 10.0 8 29
0.5 32.0 2 48.8 2
802 336 1.0 2.0 0 7.0 8 4.0 0 6.0 8 50
0.5 0 2 0 2
San Miguel Is. shelf
806 99 1.0 148.0 1.38 350% 8 142.1 1.06 10.9 8 26
0.5 56.0 2 64.0 2
805 239 1.0 162.1 oii LS.7 8 120.0 lB 14.9 8 7 5)
0.5 48.0 2 48.0 2
Santa Rosa Ridge
808 105 1.0 9.6 1.67 58) 5 0 8 12
0.5 8 2 0 2
809 225 1.0 49.9 1.95 D1 8 44.0 eri ileS) 8 Bil S
0.5 8.0 2 0) 2
Tanner Bank
815 100 1.0 12.0 DelZ 27 8 12.0 3.20 18.0* 8 30
0.5 0 2 0) 2
818 188 1.0 0 — — 1 2.0 0 7.0 8 —
0.5 0 1 8.0 2
817 519 1.0 2.0 0 7.0 8 0) — — 8 Bil 5)
0.5 0 2 0 2
* = Significant value (x? = 19.0), a= 0.05.
is interpreted cautiously. Seasonal differences in popula-
tion density were not significantly different (Mann-Whit-
ney U,, a = 0.05) at any of the sites sampled, even though
at Stations 808, 817, and 818, specimens were collected
at one season but not the other (Table 2).
At the mainland shelf sites (Stations 801, 819), most
often the densities in the 0.5-mm fraction were greater
than in the 1.0-mm fraction; in the Station 819 summer
sample nearly 99% of the specimens were in the 0.5-mm
fraction. These small specimens, mostly juveniles, may be
evidence of recruitment, but none of the other summer
samples contained such densities of juveniles.
To understand the spatial variation of P. tenuisculpta,
three separate sample sets, each collected at a different
spatial scale, were analyzed. Populations collected during
the Benchmark Study (scale = 1 km) (Table 2) generally
showed a tendency towards randomness; 13 samples were
randomly dispersed and only 4 were aggregated among
the replicates. There were no apparent effects of density
or presence of juveniles on aggregation.
Using SCCWRP data (Table 3), 10 samples were se-
lected to represent each of three zones along sewage outfall
gradients: “control,” “‘transition,’ and ‘“‘contaminated.”
Samples collected on a large scale (>1 km) indicated that
the populations of P. tenwisculpta from all zones were highly
aggregated. However, when sets of 10 replicates (scale ~
20 m) were analyzed, the populations were randomly dis-
persed except in the “transition” zone where they exhib-
ited aggregated dispersions and were most dense.
To summarize the results from these three sample sets,
it appears that patches of P. tenuisculpta may exist at
several scales. In “control” or “normal” areas, patches
were detected at the kilometer scale, but near sewage out-
falls, in the “transition” zone, patches apparently were
more densely packed. The cause of this change in popu-
lation structure in the “transition” zone is not clear.
Page 194
Table 3
Average densities and indices of dispersion for two differ-
ent sets of data on Parvilucina tenuisculpta from mainland
shelf areas. N = 10.
Mean
density
Station (No./m?) I, x?
Between zones, km scale
Normal 84 3.49 DNS.3
Transition 1304 1.64 877.0*
Contaminated 243 2.60 400.4*
Within zones, m scale
Normal
3-3 15 1.05 9.7
4-3 56 0.99 8.6
22-2 25 0.90 6.6
24-2 59 0.95 13.4
Transition
5-4 3568 1.03 115.6*
59 1844 1.03 56.5*
8-3 424 1.16 74.3*
Contaminated
7-3 25 1.23 14.6
* = Significant value (x? = 19; a = 0.05).
Diet
Parvilucina has been collected to a depth of 6 cm below
the surface (BALCOM, 1980) indicating that it may feed at
or below the sediment surface. This species has a short
100
90
80
70
60
50
40
% Total Particles
30
20
10
0 50 100 200 250 300 400 500
Mineral Particle-size
(um)
Figure 4
The Veliger, Vol. 26, No. 3
incurrent siphon and a muscular pharynx. In some of the
specimens examined, the mantle cavity and ctenidia con-
tained many large (>50 um) single mineral particles. In
three specimens examined from the offshore insular shelf
(Stations 805, 806), the pharynx contained 2-5 of these
particles (59-216 um). The digestive tracts contained
mostly detrital aggregates (aggregations of clay mineral
particles, organic material, and microbes). By volume,
mineral particles up to 100 um occurred in the gut con-
tents (Figure 4). No spatial or temporal variation in gut
contents was observed in the 20 specimens examined.
It is believed that P. tenuisculpta ingests primarily or-
ganic rich detrital aggregates from fine sediment on the
mainland shelf, but in areas where coarser sediments pre-
dominate (offshore shelves, ridges and banks) it may in-
gest larger single mineral particles, either to remove or-
ganic encrustations and microbes or to use as “mill stones”
in the pharynx to crush other food items.
Preliminary analysis of the tissues of Parvilucina has
revealed the presence of endosymbiotic bacteria that can
oxidize sulfide to obtain metabolic energy (FELBECK et al.,
1981). Populations of P. tenuisculpta living near outfalls
may utilize this alternative energy source in addition to
normal food resources, which could explain the reported
increase in size of the clams living near the outfalls (WORD
et al., 1977).
Macrofaunal Associates
Determination of the organisms associated with Parvi-
lucina tenuisculpta has been made for the two dissimilar
cs abundance
@™ volume
Average mineral particle-size distribution from guts of Parvilucina tenuisculpta collected from the insular shelves.
G. F. Jones & B. E. Thompson, 1984
Page 195
Table 4a
The numerically dominant faunal associates of Parvilucina tenuisculpta in 10 representative samples from the Huntington-
Laguna High Density Sampling Area. Abbreviations: crust. = crustacean; gastro. = gastropod; pelecy. = pelecypod; poly.
= polychaete; and oph. = ophiuroid.
Rank Name of species
Euphilomedes producta
Euphilomedes carcharodonta
Parvilucina tenuisculpta
Lumbrineris spp. (6 species)
Mediomastus californiensis
Amphiodia urtica
Prionospio cf. malmgreni
Axinopsida serricata
Glycera spp. (4 species)
Heterophoxus oculatus
Pectinaria californiensis
Macoma yoldiformis; Macoma sp.
Mysella tumida
Compsomyax subdiaphana
Tellina carpenteri
Westwoodilla caecula
Rictaxis punctocoelata
SS rs
Aman WNK DUOUAAIA UAH WN
Major Density (No./m’)
taxon (mean + SD) Frequency
crust. 1212 (+2076.1) 0.5
crust. 630 (+698.9) 0.9
pelecy. 279 (+126.9) 1.0
poly. 134 (+144.0) 0.9
poly. 130 (+115.9) 1.0
oph. 122 (+90.8) 1.0
poly. 114 (+99.0) 0.9
pelecy. 94 (+61.7) 1.0
poly. 91 (444.7) 0.9
crust. 75 (+81.6) 0.7
poly. 72 (+114.8) 0.7
pelecy. 62 (+52.8) 0.9
pelecy. 48 (+44.9) 0.9
pelecy. 3}0) (ae5)7/05)) 0.6
pelecy. 18 (419.5) 0.6
crust. 18 (+19.5) 0.6
gastro. 18 (+20.8) 0.5
Table 4b
The numerically dominant faunal associates of Parvilucina tenuisculpta in 10 representative samples from the mainland
shelf of Santa Monica Bay and San Pedro Bay. Abbreviations as in Table 4a.
Rank Name of species
Parvilucina tenuisculpta
Axinopsida serricata
Euphilomedes carcharodonta
Lumbrineris spp. (2 species)
Pectinaria californiensis
Heterophoxus oculatus
Glycera sp.
Prionospio cf. malmgreni
Tellina carpenteri
Mysella tumida
Goniada sp.
POodUdMA i YHA NUHAWN —
—
borderland environments where it is most frequent and
abundant, the mainland shelf and the Channel Islands
shelf. The faunal composition of four representative sam-
ple sets, one from each of the areas, has been examined:
on the mainland shelf, the Huntington Beach HDSA (Ta-
ble 4a) and the Santa Monica Bay and San Pedro Bay
shelves (Table 4b) and on the insular shelf, the San Miguel
HDSA (Table 4c) and the Santa Rosa HDSA (Table 4d).
The 10 samples selected to represent each area were those
in which Parvilucina was most abundant.
The numerically dominant taxa varied considerably and
only a few were dominant in all four areas; these included
Major Density (No./m?)
taxon (mean + SD) Frequency
pelecy. 789 (+734.1) 1.0
pelecy. 378 (+460.4) 0.9
crust. 158 (+174.3) 0.7
poly. 93 (+92.8) 0.9
poly. 78 (+88.4) 0.7
crust. 69 (+89.5) 0.5
poly. 50 (+49.6) 0.9
poly. 46 (+47.7) 0.6
pelecy. 22) (e229) 0.7
pelecy. 22 (+43.7) 0.5
poly. 19 (+22.4) 0.5
the polychaetes Prionospio cf. malmgreni, Lumbrineris spp.
and Glycera spp., and the mollusk Tellina carpenteri. Sev-
eral other species were numerically dominant in three of
the four areas, including the polychaete Pectinaria califor-
niensis, the crustaceans Euphilomedes carcharodonta and
Heterophoxus oculatus, and the echinoderm Amphiodia ur-
tica.
Species richness was somewhat greater at the insular
shelf locations (Santa Rosa Island sample set, 250 taxa;
San Miguel Island sample set, 198 taxa) than at the main-
land shelf locations (Santa Monica Bay-San Pedro Bay
sample set, 184 taxa; Huntington Beach sample set, 166
Page 196 The Veliger, Vol. 26, No. 3
Table 4c
The numerically dominant faunal associates of Parvilucina tenuisculpta in 10 representative samples from the San Miguel
Island High Density Sampling Area. Abbreviations as in Table 4a.
Major Density (No./m?)
Rank Name of species taxon (mean + SD) Frequency
1 Parvilucina tenuisculpta pelecy. 256 (+109.7) 1.0
2 Amphiodia urtica oph. 237 (+158.0) 1.0
3 Paraphoxus bicuspidatus crust. O(E=S226) 0.9
4 Lumbrineris spp. (7 species) poly. 50 (£56.1) 0.7
5 Prionospio cf. malmgrent poly. 48 (429.5) 0.9
6 Onuphis spp. (2 species) poly. 40 (+66.1) 0.6
7 Ampelisca pacifica crust. 37 (£22.9) 1.0
8 Heterophoxus oculatus crust. 35 (+31.8) 0.7
9 Pista sp. B; Pista sp. poly. 34 (+25.2) 0.9
10 Mediomastus californiensis poly. JP (2532) 0.5
11 Tellina carpentert pelecy. 30 (+36.8) 0.7
11 Tomburchus redondoensis pelecy. 30 (+28.1) 0.6
13 Amphissa undata gastro. 29 (+29.0) 0.7
13 Dougalopus amphicantha oph. DBS) (Ge27 5) 0.6
13 Glycera spp. (2 species) poly. 29 (+36.5) 0.6
16 Ancidea cf. longicirrata; Aricidea sp. poly. 24 (427.0) 0.8
16 Nephtys ferruginea poly. Za (GEZZ29)) 0.6
18 Notomastus spp. (2 species) poly. DDD (E299) 0.7
18 Aoroides columbiae crust. DD, (aeQ),7/)) 0.5
20 Polycirrus sp. poly. Dil (s225.183) 0.5
21 Leptochela sp. crust. ID (221.2) 0.5
22 Pholoe glabra poly. 18 (413.3) 0.7
22 Byblis veleronis crust. 18 (420.8) 0.5
24 Pectinaria californiensis poly. 16 (£14.3) 0.6
Table 4d
The numerically dominant faunal associates of Parvilucina tenuisculpta in 10 representative samples from the Santa Rosa
Island High Density Sampling Area. Abbreviations as in Table 4a.
Major Density (No./m?)
Rank Name of species taxon (mean + SD) Frequency
1 Parvilucina tenuisculpta pelecy. 602 (+488.9) 1.0
2 Lumbrineris spp. (4 species) poly. 101 (+81.6) 1.0
3) Euphilomedes carcharodonta crust. Oil (EZ UIC) 0.5
4 Tellina carpentert pelecy. 78 (478.2) 0.9
5 Nephtys spp. (3 species) poly. 54 (469.5) 0.7
6 Pholoe glabra poly. 51 (+60.6) 0.6
7 Glycera oxycephalis; Glycera sp. poly. 45 (463.5) O.7/
7 Ampelisca pugetica crust. 45 (475.3) 0.6
9 Amphiodia urtica oph. 38 (+35.2) 0.6
10 Aricidea wassi, Aricidea sp. poly. 35 (+34.9) 0.7
11 Driloneris falcata poly. 26 (+32.2) 0.5
UI Prionospio cf. malmgreni poly. 26 (+35.2) 0.5
13 Pista sp. B; Pista sp. poly. 22 (424.9) 0.6
14 Byblis veleronis crust. Dil (seBil5) 0.5
tS Artacamella hancocki poly. 18 (+16.6) 0.6
taxa). In all four areas, over half of the taxa were recorded SUMMARY anpb DISCUSSION
only once in the respective sample sets, indicating a rela- The pelecypod Parvilucina tenuisculpta is an important,
tively high level of diversity in all of these areas. widely distributed member of the benthos of the southern
G. F. Jones & B. E. Thompson, 1984
California borderland, where it is a prominent faunal ele-
ment of every major habitat type except the deep basins.
The population densities of this species were highest in
two very dissimilar environments—the insular shelf of the
northern Channel Islands and the central part of the
mainland shelf (Santa Monica Bay and San Pedro Bay).
The insular shelf is primarily a non-depositional environ-
ment. Relatively strong currents result in the winnowing
of finer detrital sediments, and the development of coarse
sediments rich in biogenic calcium carbonate components.
The area is influenced by persistent upwelling. By con-
trast, the parts of the mainland shelf where densities are
highest are in environments highly influenced by man’s
activities, particularly the release of sewage wastewaters
into the marine environment.
Parvilucina appears to exhibit little temporal variation,
but the data are indequate to make firm conclusions. Pop-
ulations of Parvilucina are patchy on a large scale (km),
but within patches they are usually randomly dispersed,
except in the areas near sewage outfalls, where the scale
of heterogeneity is approximately 20 m and densities are
the highest measured in the region. The reasons for this
change in population structure are not clear.
A diverse array of macrofaunal taxa is associated with
Parvilucina. The numerically dominant taxa varied con-
siderably from location to location, and only a few were
dominant in the four representative sample sets examined
in this study.
Parvilucina has been identified as a co-dominant ele-
ment in a faunal assemblage on the Santa ‘Rosa-Cortes
Ridge. Combining the results derived from classification
and recurrent group analysis, FAUCHALD & JONES (1979b)
identified 13 species groups from the continental border-
land. Four of these groups were on the Santa Rosa-Cortes
Ridge and Tanner Bank (Stations 805, 806, 809, 815,
816, and 818). Three of the groups were ophiuroid-dom-
inated assemblages: the Amphiodia urtica assemblage; the
Amphipholis squamata-Golfingia minuta assemblage and the
Amphiura acrystata-Ampelisca cristata assemblage. The
fourth assemblage, the Lumbrineris cruzensis-Parvilucina
tenuisculpta assemblage, is a loosely aggregated species
group that occurred at most of the offshore stations. The
principal faunal components of this assemblage are: the
polychaetes Chloeia pinnata, Decamastus gracilis, Acesta ca-
terinae, Acestra cf. assumilis, Glycera tesselata, Travisia brev-
is, and Euchone hancocki; the mollusks Amphissa undata
and Tomburchus redondoensis; the crustaceans Byblis ve-
leronis, Ampelisca pugetica, Diastylis sp. A., Maera simile,
and Photis lacia; and the echinoderm Amphiodia urtica.
Only half of these species occurred in the two mainland
shelf sample-sets, all at a frequency of 4 or less out of 10
samples, whereas 75% of them were present in the two
insular shelf sample sets at frequencies up to 7 samples
out of 10 (Tables 4a-—d).
Ecologically Parvilucina appears to be able to live in a
fairly wide range of environments populated by a large
Page 197
number of other taxa which may differ markedly from
one location to another.
The two most interesting questions concerning the ecol-
ogy of Parvilucina on the borderland are: (1) why have
the frequency and abundance of this species on the main-
land shelf increased so dramatically (from a mean of 12.0/
m? to 186.5/m?) in approximately 20 years? and (2) what
factor or factors lead to a high density of this species in
two areas that are quite dissimilar in most respects?
The load of wastewaters contributed to the marine en-
vironment has increased markedly over the last 20 years,
and this change could easily explain the elevated popu-
lation densities of Parvilucina on the affected parts of the
mainland shelf.
The insular shelf, an area of clean water, also is an
area of high organic enrichment, although the source of
this enrichment, upwelling, is very different from that on
the central portion of the mainland shelf. In another up-
welling area, at Point Conception on the mainland shelf,
population densities also are high.
Parvilucina ingests fine detrital aggregates. It may feed
at the sediment surface, or below the surface, and may
process large mineral particles to obtain food. This species
also may use endosymbiotic bacteria to oxidize sulfide near
outfalls, thereby deriving additional energy, which may
allow it to grow larger than in other areas.
ACKNOWLEDGMENTS
We wish to acknowledge the dedicated work of the entire
Bureau of Land Management Baseline and Benchmark
staff, the staff of the USC Marine Facility, the crew of
the R/V “Velero IV” (University of Southern California)
and the crew of the R/V “Thomas G. Thompson” (Uni-
versity of Washington). We particularly wish to thank
Mr. Patrick LaFollette and Mr. Jay Shrake, Associate
Marine Scientists, who identified the molluscan specimens
upon which this paper is based.
This study was sponsored by the Bureau of Land Man-
agement (United States Department of Interior) contracts
08550-CT5-52 and AA550-CT6-40 with Science Appli-
cations, Inc., La Jolla, California.
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The Veliger 26(3):199-206 (January 3, 1984)
THE VELIGER
© CMS, Inc., 1984
Hybridization of Two Populations of a Marine
Opisthobranch with Different
Developmental Patterns
by
HILLARY H. WEST
University of Maryland, College Park, Maryland 20742
JUNE F. HARRIGAN
Laboratory of Biophysics, NINCDS, NIH, at the Marine Biological Laboratory,
Woods Hole, Massachusetts 02543
AND
SIDNEY K. PIERCE!
University of Maryland, College Park, Maryland 20742
Abstract. "Two populations of the ascoglossan opisthobranch Elysia chlorotica (Gould, 1870) have
different reproductive modes. In one population, from Martha’s Vineyard, Massachusetts, veliger larvae
hatched from egg masses and fed on phytoplankton prior to metamorphosis. In the second population,
from Ipswich, Massachusetts, the majority of veligers completed development up to and including
metamorphosis in egg capsules before hatching. The Ipswich population laid egg masses with fewer
eggs, and both eggs and egg capsules were larger than those of the Martha’s Vineyard population.
Both populations can be cultured in the laboratory. The Ipswich population was cultured both in
dilute (17%c) and full strength (33%o) seawater. In laboratory culture, Ipswich larvae metamorphosed
in the egg capsule without substrate, but metamorphosis of the planktonic veligers (Martha’s Vineyard)
required the alga Vaucheria sp.
Laboratory-reared individuals from the two populations hybridized. F, egg masses had either large
Ipswich-type egg capsules or smaller Martha’s Vineyard-type egg capsules. The majority of veligers
from F,, Ipswich-type capsules remained in capsules up to metamorphosis. All veligers from F, Martha’s
Vineyard-type capsules hatched prior to metamorphosis. In F, egg masses, capsule size was intermediate
between the Ipswich and Martha’s Vineyard size classes. All F, veligers hatched prior to metamorphosis
and required Vaucheria sp. for metamorphosis.
INTRODUCTION
THOMPSON (1967, 1976) divided opisthobranch develop-
ment into three distinct categories—planktotrophic, leci-
thotrophic, and direct development. Development in each
category differs with respect to the size and number of
eggs produced and the stage of development reached when
veligers hatch from egg masses. In general, planktonic
developers produce many small eggs which hatch prior to
metamorphosis. Lecithotrophic developers produce fewer
intermediate-sized eggs which hatch prior to metamor-
' Reprint requests should be sent to this author.
phosis but after a longer embryonic period than plankton-
ic developers. Direct developers produce a much smaller
number of large eggs and remain encapsulated up to meta-
morphosis.
BONAR (1978) has refined THOMPSON’S scheme and de-
fined two variations within the category of direct devel-
opment. In some cases of direct development—referred to
as ametamorphic capsular development—embryos do not
develop into a distinct veliger stage and, therefore, do not
undergo metamorphosis before hatching as juveniles. In
other cases—referred to as capsular metamorphic devel-
opment—embryos develop into a distinct veliger stage but
do not hatch out of capsules prior to metamorphosis.
Most species of opisthobranch are limited to one of the
Page 200
reproductive patterns outlined by THOMPSON and refined
by Bonar. However, there are reports of more than one
reproductive pattern within a species (FRANZ, 1971; RI-
VEST, 1978; EysTER, 1979; CLARK et al., 1979). In only
one case (EYSTER, 1979) was an attempt made to deter-
mine whether distinct differences in developmental pat-
tern between members of a species were accompanied by
reproductive isolation.
This report compares the different reproductive pat-
terns in two populations of the euryhaline ascoglossan
opisthobranch Elysia chlorotica (Gould, 1870). Plankto-
trophic development already has been described for the
species (HARRIGAN & ALKON, 1978a). We describe here
the capsular metamorphic type of direct development in a
second population.
If this is a true case of developmental variability within
a species (poecilogony), crosses between individuals from
the different populations should produce viable hybrid
offspring. It was the purpose of this study to determine
whether the two populations could be cultured and hy-
bridized and to compare the reproductive traits expressed
in the field-collected, laboratory-reared, and hybrid gen-
erations.
MATERIALS anp METHODS
Culture of Algae
Successful culture of Elysza chlorotica depends upon the
culture of appropriate algal food sources for both adult
and larval stages. Adults feed on various species of the
alga Vaucheria; the veligers require unicellular algae. Mats
of substrate, containing filaments of Vaucheria compacta
(Collins) Collins, were collected in salt marshes and placed
in petri dishes moistened with seawater. The mats were
kept in an incubator at 15°C on an 18-h light: 6-h dark
cycle. Light was supplied by six fluorescent bulbs. A sec-
ond species, Vaucheria litorea C. Agardh, also collected
from salt marshes, was grown submerged in “f/2” algal
medium of GUILLARD (1975) under the same conditions.
The unicellular alga Chroomonas (strain 3C), used to feed
the veligers, was cultured in “f/2” medium under the
same conditions as Vaucheria.
Culture of Encapsulated Larvae
Approximately 100 adult animals collected from Ips-
wich, Massachusetts were placed in glass baking dishes
containing seawater of salinity 33 parts per thousand (%o)
which was changed every other day. The animals were
kept in an incubator at 18-19°C on a 12-h light: 12-h
dark cycle. Light was provided by four fluorescent bulbs.
Vaucheria compacta, often attached to marsh sediment, was
placed with the animals as a food source. Egg masses were
collected daily and each egg mass was transferred to a
small, glass petri dish containing seawater filtered through
a Millipore membrane (0.45 um pore). In order to classify
The Veliger, Vol. 26, No. 3
the development type, the following observations and mea-
surements were made: (1) the number of eggs per egg
mass was determined in six egg masses by counting the
number of eggs in 5 mm of egg mass, dividing by 5, and
multiplying the result by the total length of egg mass; (2)
the size of five uncleaved eggs and their capsules was
measured using an ocular micrometer and compound light
microscope; and (3) the number of days to veliger stage,
eyespot formation, and metamorphosis was recorded. In
addition, adult sizes were recorded as unrelaxed length
using a millimeter rule.
Elysia chlorotica inhabits low salinity marshes. In the
course of collecting slugs we measured salinities from 3 to
32%o. Because this is such a wide range of salinities, the
effect of salinity on development was investigated. Adults
from Ipswich, Massachusetts were kept in dilute seawater
(17%c). Egg masses were collected from these adults and
the pattern of development was observed to determine the
effect salinity had on development.
Culture of Planktonic Veligers
Ten adults collected from Menemsha Pond, Martha’s
Vineyard, Massachusetts in the fall of 1979 survived over
winter and laid egg masses in the spring of 1980. Egg
masses were isolated and veligers maintained up to meta-
morphosis according to the general methods described by
HARRIGAN & ALKON (1978a). Measurements of (1) the
number of eggs per egg mass, (2) the size of eggs and egg
capsules, and (3) the size of adults, were made as previ-
ously described. The time required for veligers to reach
various stages of development was determined. Veligers
were ready to hatch shortly after the development of a
black pigment band on the dorsal surface behind the ve-
lum. At this stage, the egg masses were teased open, and
the veligers released were washed in seawater filtered
through Millipore membranes (0.22 um pore) with Ri-
fampicin added (5 mg/L). Approximately 1000 veligers
were transferred to each of three 1-liter beakers contain-
ing 800 mL of filtered (0.22 um) seawater containing Ri-
fampicin (5 mg/L). Cetyl alcohol was sprinkled on the
surface of the culture to prevent the veligers from being
caught in the surface tension (HURST, 1967). Beakers were
covered with plastic to minimize contamination by dust.
Seawater in the beakers was changed three times a week.
To separate veligers from culture water, cultures were
gently poured through 44-uwm plankton netting stretched
across the diameter of a piece of plastic (PVC) pipe. The
pipe was held upright in a finger bow] filled with seawater
such that the plankton net and veligers were always below
the surface of the water. Veligers concentrated above the
plankton netting were washed with fresh seawater then
transferred with a pipette to beakers of fresh seawater and
Rifampicin.
The veligers were fed Chroomonas six days a week.
After determining the cell count of algal cultures with a
hemocytometer, a sufficient volume of algal cells was added
H. H. West et al., 1984
Page 201
to the veliger cultures to yield a final cell count of 3 to 5
cells/uL.
The veligers were judged competent to metamorphose
on the basis of three criteria: (1) development of eyespots;
(2) development of a propodium; and (3) enlargement of
the black pigment patch initially located immediately pos-
terior to the velum over the entire dorsal surface of the
larva. Once judged competent, groups of 50 veligers were
placed in culture dishes containing 100 mL of coarse-
filtered (1 wm) seawater and filaments of Vaucheria. Ve-
ligers attached to the algae and metamorphosed. Subse-
quently juveniles were transferred to larger culture dishes
and eventually into aquaria. The juveniles were contin-
uously fed Vaucheria compacta because it was the most
abundant Vaucheria species. The number of veligers sur-
viving up to metamorphosis and the number that subse-
quently metamorphosed were determined.
Metamorphosis on Different Algal Substrates
A separate experiment was performed to determine
whether other substrates could be used for metamorphosis.
One hundred veligers were placed in culture dishes with
either Vaucheria compacta, V. litorea, Enteromorpha sp., or
Bryopsis plumosa (Hudson) C. Agardh (all collected from
Martha’s Vineyard), and the number of metamorphosed
juveniles was counted. Enteromorpha sp. was chosen be-
cause it represents a major part of the pond flora. Bryopsvs
is not common in the pond but one species of this genus
has previously been identified as a food source for other
ascoglossan species (GREENE, 1970).
Laboratory Crosses—Parental, F,, and F, Generations
Parents for the crosses were the offspring from egg
masses laid by field-collected Ipswich and Martha’s Vine-
yard adults. These offspring were raised according to the
culture procedures described above except that all animals
were raised at room temperature (25°C). Measurements
of the characteristics of parental egg masses were made
on the egg masses collected from crosses of the field-col-
lected adults—Ipswich x Ipswich and Martha’s Vine-
yard x Martha’s Vineyard. Length of egg capsules, length
of veliger shells, and the days to hatching after egg-mass
deposition were recorded in 10 egg masses of each type.
Directly following metamorphosis, 10 offspring from each
developmental type were isolated. Each Ipswich offspring
was placed with a Martha’s Vineyard offspring to form
a mating pair (Ipswich x Martha’s Vineyard). Because
the species is hermaphroditic, each individual in a cross
could serve as both male and female. Egg masses from
these parental mating pairs were the F, egg masses that
gave rise to the F, adult generation.
Each F, egg mass was scored according to parental
affinity. A Martha’s Vineyard-type F, egg mass was de-
fined as having all egg capsules of small length and veli-
gers that hatched with no eyespots or propodium. An Ips-
wich-type egg mass had large capsules and veligers that
either hatched with eyespots and propodium late in de-
velopment or metamorphosed in capsules. Measurements
of capsule length, veliger shell length, and days to hatch-
ing were made from 10 F, Martha’s Vineyard-type egg
masses and 10 F, Ipswich-type egg masses. Offspring from
F, Martha’s Vineyard-type egg masses and F, Ipswich-
type egg masses were isolated directly following meta-
morphosis. Ten mating pairs were formed by placing one
offspring from a Martha’s Vineyard-type egg mass with
one offspring from an Ipswich-type egg mass (Ipswich
F, x Martha’s Vineyard F,). Egg masses from these F,
crosses were the F, egg masses that gave rise to the F,
generation. Measurements of capsule length, veliger shell
length, and days to hatching were made on 10 of these F,
egg masses.
To determine whether the slugs self-fertilized, newly
metamorphosed offspring from parental egg masses of each
developmental type were isolated and observed for possi-
ble egg mass deposition. In addition, some newly meta-
morphosed individuals from parental egg masses of each
developmental type were grouped together (Ipswich x
Ipswich and Martha’s Vineyard x Martha’s Vineyard).
The F, and F, generations produced by these intrapopu-
lation crosses served as controls to monitor the effects of
laboratory culture on developmental type.
RESULTS
Culture of Encapsulated Larvae
Developmental characteristics of the population from
Ipswich, Massachusetts are listed in Table 1. Field col-
lected animals had a mean length of 7.60 mm. The mean
number of eggs/egg mass was 175.67. A distinctive fea-
ture of this development type was the relatively large di-
ameter of the egg capsule in relation to egg diameter. The
mean capsule length of 309.00 um was three times the
mean diameter of the egg (96.00 wm). In addition, the
capsules and embryos were surrounded by a thick gelat-
inous layer. There was a statistically significant decrease
in development time for egg masses raised in dilute sea-
water (Table 2). At both salinities the embryos reached
the veliger stage in approximately three days. All veligers
eventually developed black pigment bands on the dorsal
surface of the velum. Eyespots appeared in larvae ap-
proximately six days after egg mass deposition in dilute
seawater and nine days after deposition in full strength
seawater. About two weeks were required for eggs in full
strength seawater to develop through metamorphosis.
Usually the encapsulated veligers would cast off the
shell inside the capsule and crawl away as metamorphosed
juveniles. However, some veligers from egg masses in full
strength and dilute seawater hatched before metamorpho-
sis while others in the same egg mass remained two to
three days longer in the capsule and metamorphosed be-
fore hatching. We were not able to follow the fate of the
Page 202
The Veliger, Vol. 26, No. 3
Table 1
Developmental features of two Elysia chlorotica populations. All values expressed as mean + SD, followed by sample
size in parenthesis. * Significant at the 0.01 level; ** 20 veligers observed in one culture only, in all other cases embryos
were observed in more than one egg case.
Ipswich population
Martha’s Vineyard
(encapsulated population
metamorphosis) (planktonic) t-statistic
Length of field-collected animals 7.60 + 2.58 mm (133) 20.01 + 8.00 mm (233) 117/56
Eggs per egg mass I7/S.O7 z= 112.53 (G6) 8901.5 + 7257.9 (16) *2.68
Diameter of egg 96.00 + 8.22 um (5) 79.33 + 2.58 um (15) *7.18
Length of egg capsule 309.00 + 8.22 um (5) 164.00 + 12.42 um (15) OST
Days to veliger after deposition 3.00 + 0 (93) 2.88 + 0.32 (34) *3,49
Days to eyespot after deposition 9.00 + 0 (93) **13-15 (20) =
Days to metamorphosis after deposition 13.83 + 8.60 (93) 21.56 + 0.50 (34) *49 18
early hatching veligers. After hatching from the egg masses,
juveniles would begin to feed on Vaucheria filaments and
the previously clear digestive gland turned a dark green
color.
Culture of Planktonic Veligers
Developmental characteristics of the population from
Martha’s Vineyard are also listed in Table 1. Field-col-
lected animals had a mean length of 20.01 mm. The mean
number of eggs/egg mass was 8901.5. The mean egg di-
ameter was 79.33 wm or about half the mean capsule
length, which was 164.00 wm. The egg masses lacked the
thick gelatinous layer of the encapsulated metamorphosis
type. Embryos reached the veliger stage in approximately
three days and developed dorsal black pigment bands be-
fore hatching. After hatching on day 7 or 8 following egg
mass deposition, veligers spent 14 to 15 days feeding on
unicellular algae prior to metamorphosis. Eyespots devel-
oped 13 to 15 days after egg mass deposition. As the ve-
ligers matured a propodium developed, and just prior to
metamorphosis the black pigment band spread to cover
much of the dorsal surface of the animal. When the pig-
mented veligers were presented with filaments of Vauche-
ria, they settled on the algal filament, velum down, with
the shell lifted upwards. Metamorphosis took place over
a period of one to two days. Occasionally, metamorphosis
occurred spontaneously in culture beakers before the ve-
ligers were exposed to the algal substrate.
Metamorphosis on Different Algal Substrates
Of the 100 veligers placed in each of the culture dishes
with the different algal species, 50 to 60 metamorphosed
in the dishes containing either Vaucheria compacta or V.
litorea. Only one metamorphosed juvenile was found in
either of the culture dishes containing Enteromorpha or
Bryopsis.
Statistical Comparison of the Two Populations
The results of the two-tailed “Student’s” f-tests com-
paring the developmental characteristics of the two pop-
ulations are listed in Table 1. For all developmental char-
acteristics compared there was a statistically significant
difference between the two populations (P < 0.01).
Laboratory Crosses—Parental, F,, and F, Generations
Egg capsule length and shell length at hatching: Figure
1 shows the distribution of egg capsule lengths and shell
lengths at hatching measured from egg masses deposited
by the parental, F,, and F, generations. The F, generation
consisted of a total of 25 morphologically Ipswich-type
egg masses (Ipswich F,) and 34 morphologically Martha’s
Vineyard-type egg masses (Martha’s Vineyard F,). Fig-
ure 1 illustrates that both capsule length and shell length
of the F, egg masses were distributed bimodally; each set
of measurements corresponded closely to those of the sim-
ilar parental generation.
Table 2
Developmental features of Elysia chlorotica (Ipswich population) at two salinities. All values expressed as mean + SD,
followed by sample size in parenthesis. * Significant at the 0.01 level.
Salinity at 33%o
Salinity at 17%o t-statistic
Days to veliger after deposition 3.00 + 0 (93) Doh) 2e (04'S) (2) #713},5)1
Days to eyespot after deposition 9.00 + 0 (93) BOY ze O79 (Ui) *106.55
Days to metamorphosis after deposition 13.83 + 0.86 (93) SDS zz O:657/ (iQ) eal eeAl
H. H. West et al., 1984
PARENTAL GENERATION ( MARTHA'S VINEYARD)
F1 GENERATION
% OF SAMPLE
Martha's Vineyard - like
@ee@
y LF XS o—0%,0
Ipswich-like
soe.
68Cl
e e
F2 GENERATION
R
Page 203
----- @ SHELL LENGTH
o—o CAPSULE LENGTH
Fe aCe
/ \
b
e
2 3 ee ee
©.9--0 pee % -e’
150 200 250
300 350 400 450
LENGTH (ym)
Figure |
Relationship between shell length (um) at hatching and egg capsule length (um) for each population. Note especially
the bimodal distributions of shell and capsule lengths in the F, generation and convergence of these characters in
the F, generation.
In contrast to the F, egg masses, the 48 F, egg masses
could not be classified as either Ipswich-type or Martha’s
Vineyard-type. Both capsule length and shell length at
hatching are distributed unimodally (Figure 1), with the
means falling between those of the parental and F, gen-
erations (Table 3). In all generations, egg capsule sizes
were more variable than shell lengths.
Egg capsule lengths and shell lengths for all five pop-
ulations combined were highly significantly different when
analyzed using one-way ANOVA for unequal sample sizes
(SNEDECOR & COCHRAN, 1967) (F,3;; = 3027.3, P = 0.01
for capsules; F,,;; = 200.4, P <= 0.01 for shells). Subse-
quent application of the Newman-Keuls modification of
the Q-test for significant differences between means showed
that F, capsule lengths and shell lengths differed signifi-
cantly from those of both the Martha’s Vineyard F, and
Ipswich F, populations (D = 11.1 wm for shells, P < 0.05;
D = 20.9 um for capsules, P < 0.05; and Figure 2). The
Martha’s Vineyard F, and parental generations also dif-
fered significantly, but the Ipswich F, and the Ipswich
parental generations did not (Figure 2).
Hatching and metamorphosis: Table 4 lists the devel-
opmental stage at hatching and the time from egg mass
Table 3
Laboratory crosses of Elysia chlorotica: egg capsule length and shell length per generation. All values expressed as mean
+ SD, followed by sample size in parenthesis.
Generation
Parental—Maartha’s Vineyard
Parental—Ipswich
F,—Maartha’s Vineyard-type
F ,—Ipswich-type
F,
Capsule length (um)
OZ
348.8
167.2
330.6
2ND).3)
Shell length (wm)
+ 36.3 (100) 145.8 + 10.6 (80)
+ 24.3 (100) 216.7 + 7.9 (100)
+ 10.2 (30) 134.1 + 8.7 (30)
+ 23.8 (30) 220.6 + 6.6 (30)
+ 28.9 (100) 176.5 + 16.2 (100)
Page 204
@---@ x SHELL LENGTH
x CAPSULE LENGTH
* SIZE DIFFERENCE IS SIGNIFICANT (p< 0.05)
]
GENERATIONS
100 150 200 230 300 350
MEAN LENGTH (pm)
Figure 2
Mean shell and capsule lengths per generation; asterisk indicates
means significantly different at P < 0.05. P, parental generation;
F,, first generation; F,, second generation; M, Martha’s Vine-
yard (P) or Martha’s Vineyard-like (F,) population; I, Ipswich
(P) or Ipswich-like (F,) population.
deposition to hatching for each population. The trend in
the crosses is toward reduction of time spent in intracap-
sular development and the production of planktotrophic
veligers. Although the F, veligers are significantly larger
than the Martha’s Vineyard parental veligers (Table 3
and Figure 2), they hatch in about the same amount of
time—five to seven days for the Martha’s Vineyard gen-
eration versus five to nine days for the F, generation (Ta-
ble 4). The F, veligers also differ from the Martha’s Vine-
yard parental veligers because eyespots are found in a
variable fraction of the hatchlings from each egg mass.
The days from egg mass deposition to hatching were
significantly different overall for the F, and F, populations
The Veliger, Vol. 26, No. 3
(F,., = 105.6, P = 0.01). By the Newman-Keuls Q-test,
the number of days to hatching in the F, generation, which
appears intermediate in time between the Martha’s Vine-
yard and Ipswich F, populations, differed significantly
from days to hatching of both the Martha’s Vineyard-
type F, and Ipswich-type F, populations (D = 0.2 days,
P < 0.05; and Table 4).
Self-fertilization and control crosses: Some of the newly
metamorphosed individuals that were isolated from pa-
rental egg masses did lay egg masses. However, develop-
ment of eggs in these egg masses was abnormal in both
populations and no juveniles were produced.
All F, and F, egg masses produced by intrapopulation
crosses (Ipswich xX Ipswich and Martha’s Vineyard x
Martha’s Vineyard) were of the parental developmental
type. That is, F, egg masses laid in the Ipswich crosses
had large capsules and most juveniles hatched from egg
capsules following metamorphosis; F, egg masses laid by
the Martha’s Vineyard crosses had small capsules and
hatched as veligers without eyespots.
DISCUSSION
Compared to other opisthobranchs, Elysza chlorotica 1s cul-
tured with relative ease. First, the culture of direct devel-
opers is simple compared to planktonic developers because
they do not require unicellular algae for growth and spe-
cial techniques to change culture water. Also, in this study,
normal development of direct developers took place even
with a significant change in salinity.
Although it is more difficult to feed and clean them, the
planktotrophic veligers of this species have a short plank-
tonic stage when compared with 34 to 40 days in other
opisthobranchs (SWITZER-DUNLAP & HADFIELD, 1977;
HARRIGAN & ALKON, 1978b; CHIA & Koss, 1978). The
key to the successful culture of the planktonic veligers is
the identification of the substrate for metamorphosis, in
Table 4
Laboratory crosses of Elysia chlorotica: developmental stage at hatching and time to hatching in each generation.
Egg
masses/ Days to hatching
gener- after deposition
Generation ation Hatching stage (mean + SD)
Parental—Maartha’s Vineyard 10 100% veligers 58) se 11,0)
(no eyespots, no propodium)
Parental—Ipswich 10 100% juveniles 10.67 + 0.5
F,—Martha’s Vineyard-type 34 100% veligers 5.4 22 Of
(no eyespots, no propodium)
IF ,—Ipswich-type 25 27% veligers with eyespots and propodium; 10.2 + 2.0
59% mixed veligers and juveniles;
17% juveniles only
1B) 48 100% veligers, some with eyespots 7.0 + 0.8
and propodium
H. H. West e al., 1984
Page 205
this case, Vaucheria. It is not surprising that Vaucheria is
the substrate for metamorphosis because adult digestive
cells contain symbiotic chloroplasts which originate from
Vaucheria (GRAVES et al., 1979; WEST, 1979).
There are two important differences between direct de-
velopment and planktotrophic development among opis-
thobranch species. First, in the direct development of any
species, veligers require a stored food source because they
do not feed on unicellular algae. Food reserves are stored
as yolk in the egg. Consequently, opisthobranchs with
direct development usually have large eggs, ranging from
205 to 400 wm in diameter (THOMPSON, 1967, 1976).
Although the population with direct development in this
study has a larger egg size than the population with
planktotrophic veligers, the average diameter is only 96
um. It is possible that food reserves may be stored in
extraembryonic albumen in addition to yolk, which could
account for the large capsule size in the direct developers.
CLARK & JENSEN (1981) have proposed that large cap-
sules and extraembryonic nutrients are typical of direct
development in all ascoglossans.
A second difference accompanying direct development
is that encapsulated metamorphosis takes place without
external cues (BONAR, 1978). Models of metamorphosis
of planktonic larvae involve some precise chemical cue
which triggers a neuronal response in mature veligers
(HADFIELD, 1978). Differences between Ipswich and
Martha’s Vineyard veligers could present an interesting
problem in developmental neurobiology. It may be signif-
icant that both the present study and the study by HarrI-
GAN & ALKON (1978a) found that not all Martha’s Vine-
yard veligers required Vaucheria for metamorphosis. If
planktonic development was the original development type
of the species, it could be that populations with encapsu-
lated metamorphosis developed from the certain percent-
age of all veligers which could metamorphose without ex-
ternal cue.
There are two other species of opisthobranch where the
existence of more than one developmental pattern in the
species is described in some detail. In the case of both
Tenellia pallida (Alder & Hancock) (EYSTER, 1979) and
the ascoglossan Elysia cauze (Marcus, 1957) (CLARK et
al., 1979) the two developmental patterns appeared to oc-
cur within single populations. For EL. cauze the patterns
were separated on a seasonal basis and no laboratory
crosses were done. In the case of 7. pallida, crosses were
made by pairing field-collected individuals of unknown
reproductive type. All F, offspring were not intermediate
in character but were of one or the other developmental
type in the population. This is similar to the parental type
F, generation in our study of Elysia chlorotica. Unfortu-
nately, in the 7. pallida study no F, generation was pro-
duced.
The results of the hybridization of the two Elysia chlo-
rotica populations were unexpected. The continuous dis-
tribution of capsule length and shell length in the F, gen-
eration suggests that these characters are controlled by
multiple genes. However, this type of distribution is usu-
ally expected for the F, hybrid generation not the F, gen-
eration (FALCONER, 1960). Two possible explanations for
these results are: (1) the control of certain developmental
traits by maternal genes and (2) self-fertilization.
In the case of maternal control it is possible that the
morphology of F, and F, egg capsules depends on the
maternal genotype regardless of the genotype of egg and
veliger. This model would account for the appearance of
Ipswich-type and Martha’s Vineyard-type capsules in the
F, generation because they were deposited by nonhybrid
parents, and intermediate or hybrid capsule types in the
F, generation because they were deposited by hybrid par-
ents. Based on this argument it is more difficult to explain
why hatching time is intermediate in the F, and not in
the F, generation. In the case of opisthobranchs, hatching
from egg masses is thought to depend on the production
of some enzyme by the veliger (DAvis, 1968). If this is
the case, hatching should depend on veliger genotype.
However, it is possible that a maternal control of food
reserves in egg yolk or capsule albumen, as well as a
maternal control of capsule structure, could influence when
veligers hatch.
The persistence of parental characters in the F, gen-
eration also could be explained either by selfing in the
parental generation while the F, outcrossed or by selfing
in both the parental and F, generations with an eventual
breakdown of parental characters in the F, generation.
There is one report of self-fertilization in another asco-
glossan (KAWAGUTI & YAMASU, 1961). However, because
in our laboratory cultures, egg masses laid by isolated
individuals developed abnormally, it seems that self-fer-
tilization alone could not explain the maintenance of ma-
ternal characters in the F, generation.
The production of viable F, and F, offspring from the
crosses does not prove that the two populations are ac-
tually one species. More extensive genetic studies would
have to be performed to determine whether these popu-
lations actually represent one species. However, the re-
sults do suggest that crosses between populations could
occur in the field and that other populations could exhibit
developmental characteristics different from the Ipswich
or Martha’s Vineyard populations. So far, descriptions of
reproductive variation of Elysza chlorotica are limited to
the two geographically separated populations in this study.
It is not known whether populations with the character-
istics of the F, and F, generations of this study occur
naturally. Although EF. chlorotica has a geographic range
from Nova Scotia to Florida (Marcus, 1980), descriptions
of development in other populations are limited to one
report describing planktotrophic development in Chesa-
peake Bay and Virginia (VOGEL, 1978). Further studies
are underway to identify the extent of variation in other
populations and to find whether any correlations exist
between certain habitats and development types.
Page 206
ACKNOWLEDGMENTS
The authors wish to thank Dr. E. E. Webber for assis-
tance in identifying Vaucheria species. This work was sup-
ported by NIH grant #GM23731 to S. K. Pierce. Ad-
ditional support was provided by the Intramural Research
Program of the National Institute of Neurological and
Communicable Diseases and Stroke, NIH. The first au-
thor gratefully acknowledges support from the Lerner
Foundation for Marine Research of the American Mu-
seum of Natural History. This is contribution #198 from
the Tallahassee, Sopchoppy and Gulf Coast Marine Bi-
ological Association.
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The Veliger 26(3):207-213 (January 3, 1984)
Tes VEL
© CMS, Inc., 1984
The Opisthobranch Mollusks of Humboldt
County, California
WILLIAM B. JAECKLE
Department of Biological Sciences, University of Southern California,
University Park, Los Angeles, California 90089
Abstract. Sixty-eight species of opisthobranch Mollusca are documented from twenty-one collection
sites in Humboldt County, California. The sighting of Hancockia californica represents a geographical
range extension. Aspects of the biology of certain species are discussed.
INTRODUCTION
SINCE 1968, MANY annotated checklists and natural his-
tory reports discussing the opisthobranch gastropods from
California counties and other geographical localities have
been published (SPHON & LANCE, 1968; ROLLER & LONG,
1969; ROLLER, 1970b; GOSLINER & WILLIAMS, 1970,
1973b; BERTSCH et al., 1972; HOLLEMAN, 1972; GODDARD,
1973; BEHRENS & TUEL, 1977; NYBAKKEN, 1978; BEHR-
ENS, 1980b). From these reports, our knowledge of these
mollusks has increased greatly, but none of these works
examines the opisthobranch fauna from areas north of
Marin County, California (latitude 38°17'38”N; longi-
tude 123°00’05”W). As a result, the opisthobranch fauna
of northern California is poorly documented and the num-
ber of publications dealing specifically with the opistho-
branch gastropods of Humboldt County is extremely lim-
ited. WICKSTEN & DEMARrRTINI (1973) described a new
anthozoan prey species of the dendronotacean nudibranch
Tochuina tetraquetra (Pallas, 1788) from Trinidad Bay;
McDONALD (1977) noted a photograph of Crzmora coneja
Marcus, 1961, reportedly from Humboldt County; and
JAECKLE (1981a, b) reported geographical range exten-
sions for several nudibranch species. Three marine biota
surveys have been conducted in certain littoral and sub-
littoral localities in Humboldt County (BoypD & DE-
MarTINI, 1977; Boyp, 1979; BoyD & SJOGREN, 1979),
and these list the opisthobranch species from their respec-
tive areas.
This paper presents the results of a three-year exami-
nation of the gastropod subclass Opisthobranchia in
Humboldt County and a compilation of data from pre-
viously published works. Personal sightings have been
augmented by specimens collected by the faculty and grad-
uate students of the Department of Biological Sciences,
Humboldt State University, Arcata, California.
Humboldt County (Figure 1) is located in northwestern
California, and the coastline is characterized by rocky cliffs,
expanses of rocky littoral areas, sandy beaches, and one
major estuary, Humboldt Bay. A total of 57 collection
trips, primarily during the months of June, July and Au-
gust, were made at 14 collection sites; specimens supplied
from additional localities and previously published ac-
counts bring the cumulative total to 21 collection sites
(Table 1; Figure 1). Topographically, these sites range
from an area of extreme oceanic exposure (e.g., North
Jetty) through semi-protected rocky habitats (e.g., Trini-
dad Bay) to calm, floating dock communities and Zostera
marina beds of Humboldt Bay (7.e., Fields Landing and
the Somoa Boat Ramp).
OCCURRENCE anp DISCUSSION oF
HUMBOLDT COUNTY
OPISTHOBRANCH MOLLUSKS
Except where noted, all examined specimens were col-
lected from littoral localities. In only one instance was
bathymetric data obtained for specimens collected in sub-
littoral areas, denoted by an (s). The sites of collection are
keyed by numbers (Table 1) with each individual species
in the list below. An asterisk (*) denotes a geographical
range extension; a (+) indicates that the collection data
were obtained from the Humboldt State University ma-
rine invertebrate museum collection.
CEPHALASPIDEA
ACTEONIDAE
Rictaxis punctocaelatus (Carpenter, 1864)
Wy WSs
Page 208
AGLAJIDAE
Aglaja ocelligera (Bergh, 1894) +
8(s).
Melanochlamys diomedea (Bergh, 1894)+
8(s).
ANASPIDEA
APLYSIIDAE
Aplysia californica Cooper, 1863
Aplysia californica is reportedly very common in the dis-
charge canal of the Humboldt Bay Power Plant (David
Behrens, Pacific Gas & Electric Company, personal com-
munication); however, no specimens were sighted during
this study.
Phyllaplysia taylor: Dall, 1900
13, 17. Phyllaplysia taylort is commonly epiphytic on
the marine angiosperm Zostera marina Linnaeus in Hum-
boldt Bay. Nidosomes of P. taylort have been found on
Zostera from May through October and young specimens
are common in October and November.
NOTASPIDEA
PLEUROBRANCHIDAE
Berthella californica (Dall, 1900)
3, 4. Many members of the notaspidean family Pleu-
robranchidae are known to produce epidermal acidic se-
cretions aS an active defense mechanism (THOMPSON,
1976a). A field observation suggests that Berthella califor-
nica has the capacity to secrete a repellent material. At
Palmer’s Point (#4), a specimen of the carnivorous aster-
oid Pycnopodia helianthoides (Brandt, 1835) was observed
crawling onto a specimen of B. californica. After approx-
imately a 30-second time interval, the Pycnopodia speci-
men moved rapidly away from the pleurobranch. An ex-
amination of the area immediately following this
interaction revealed no other organisms that could con-
ceivably have elicited this response by the asteroid.
Pleurobranchaea californica MacFarland, 1966
19(s). One specimen collected by a commercial fisher-
man at 550 m depth.
SACOGLOSSA
STILIGERIDAE
Alderia modesta (Lovén, 1844)
9. iO, ii.
Aplysiopsis smithi (Marcus, 1961)
5. This sacoglossan species was feeding on an uniden-
tified filamentous chlorophyte in a small supralittoral
fringe tidal pool. Among the algal filaments were numer-
ous nidosomes of A. smith: (shape of nidosome described
by GONoR, 1961).
The Veliger, Vol. 26, No. 3
a
SES
Arcata
Bay
Figure 1
Humboldt County, California. Numbers indicate sites of collec-
tion (see text). A. Humboldt Bay; B. Humboldt County.
Placida dendritica (Alder & Hancock, 1843)
3. 6.
Stiliger fuscovittatus Lance, 1962
8.
NUDIBRANCHIA
Doridacea
OKENIIDAE
Ancula pacifica MacFarland, 1905
3, 4, 16.
Hopkinsia rosacea MacFarland, 1905
4. A single specimen of this suctorian dorid was found
on its prey, the bryozoan Eurystomella bilabiata (Hincks,
1884) (McBETH, 1971). The dorsal papillae of H. rosacea
are reportedly tall, slender, and simple (BEEMAN & WIL-
LIAMS, 1980; BEHRENS, 1980a; MCDONALD & NYBAKKEN,
1980); however, many of this specimen’s papillae were
branched and/or apically bifurcated as described by
MaAcFaRLAND (1906).
ONCHIDORIDIDAE
Acanthodoris nanaimoensis O’ Donoghue, 1921
1-2, 4, 6, 6(s), 16.
W. J. Jaeckle, 1984
Table 1
Geographical localities.
1-2 Redwood National Park
3 Palmer’s Point
4 Abalone Beach
5 Omenoku Point
6 Trinidad Bay
ih Luffenholtz Beach
8
Arcata Bay, Humboldt Bay (=North Bay of JAECKLE, 1981b)
9 Freshwater Slough
10 Park Street Marsh
11 Park Street Slough
12 Eureka Boat Harbor
13 Somoa Boat Ramp
14 North Jetty
15 Elk River Slough
16 Humboldt Bay Coast Guard Station (HBCGS)
17 South Spit, South Bay, Humboldt Bay
18 Fields Landing
19 Eel River Submarine Canyon
20 Cape Mendocino
21 Point Delgada
22-23 King Range
Page 209
Latitude Longitude
41°16'10"N 124°06'35”W
to
41°22’41"N 125°04'12”W
41°07'21"N 124°09'32”W
41°07'20’N 124°09'32”W
41°04'01"N 124°09'19”W
41°03'07"N 124°07'51”W
41°02'51"N 124°07'04”W
~40°51'N ~124°08'W
40°48/17"N 124°07'W
40°48'17"N 124°07’W
40°48'17"N 124°07’'W
40°48'15"N 124°10'41”W
40°46'21"N 124°18'39”W
40°46'09"N 124°14'15”W
40°46'00’N 124°11'57”W
40°45'55’"N 124°13'04”W
40°44'00’N 124°12'31”W
40°43'26"N 124°13'20”W
~40°41"N ~124°40'W
40°26'44"N 124°24'43”"W
40°01'27"N 124°04'17”W
40°19'38"N 124°20'14”W
to
39°59'38"N 123°59'46”W
Acanthodoris rhodoceras Cockerell in Cockerell & Eliot,
1905
16.
Adalaria sp.
16. The radular and external morphology of this onchi-
dorididean species correspond with that of Adalaria sp.
(BEHRENS, 1980a, fig. 138) and to a specimen supplied
by Sandra Millen (University of British Columbia). The
orange ground color of the specimens collected in Hum-
boldt County differs significantly from the white color-
ation of northern forms. This species is found exclusively
on the orange anascan cheilostome bryozoan Lyrula hip-
pocrepis (Hincks, 1882), upon which it feeds. Nidosomes,
deposited directly on Lyrula, have been found in August
and October.
Onchidoris bilamellata (Linnaeus, 1767)
3, 4, 6(s), 16. This species was sighted on or near the
barnacles Balanus crenatus Bruguire, 1789, or B. glandula
Darwin, 1854. Nidosomes were found in littoral areas in
January and July; a large sublittoral population in Trin-
idad Bay spawns in late summer (Tim Stebbins, Univer-
sity of Southern California, personal communication).
Hurst (1967) reported that nidosomes of O. bilamellata
are extremely common in Washington during the winter
months.
Onchidoris hystricina (Bergh, 1878)
B.A by I. 1G;
Onchidoris muricata (Miller, 1776)
4, 6, 16.
TRIOPHIDAE
Triopha catalinae (Cooper, 1863)
3, 4, 6, G(s).
Triopha maculata MacFarland, 1905
3), 44 O; 1,
Crimora coneja Marcus, 1961
This species was not sighted during the study; however,
McDONALD (1977) noted a photograph of Crimora coneja
reportedly from Humboldt County.
Aegires albopunctatus MacFarland, 1905
3, 4, 6(s).
Laila cockerell MacFarland, 1905
4,
POLYCERIDAE
Polycera atra MacFarland, 1905
8.
Page 210
Polycera zosterae O’Donoghue, 1924
14. On the bryozoan Dendrobeania laxa (Robertson,
1905).
CADLINIDAE
Cadlina flavomaculata MacFarland, 1905
4.
Cadlina luteomarginata MacFarland, 1905
3, 4, 6, 6(s), 16.
Cadlina modesta MacFarland, 1966
4.
ACTINOCYCLIDAE
Hallaxa chani Gosliner & Williams, 1975
Bards
ALDISIDAE
Aldisa cooper: Robilliard & Baba, 1972
6.
Aldisa sanguinea (Cooper, 1863)
33
ROSTANGIDAE
Rostanga pulchra MacFarland, 1905
1-2, 3, 4, 6, 6(s), 16, 22-23.
ARCHIDORIDIDAE
Archidoris montereyensis (Cooper, 1863)
1-2, 3, 4, 6, 6(s), 12, 16, 17. Specimens sighted in rocky
littoral areas possessed the typical yellow to orange ground
color with scattered black notal pigmentation. However,
individuals examined from soft bottom areas of Humboldt
Bay exhibited a dark yellow-brown to dark gray ground
coloration. In several instances, the ground coloration was
sufficiently dark to nearly obscure the black notal pig-
mentation.
Archidoris montereyensis has been seen feeding on the
sponge Halichondria panicea (Pallas, 1766).
Archidoris odhnert (MacFarland, 1966)
6, 6(s).
DISCODORIDIDAE
Anisodoris nobilis (MacFarland, 1905)
3, 4, 6, G(s), 16.
Diaulula sandiegensis (Cooper, 1863)
1-2, 3, 4, 6, 6(s), 14, 16, 22-23.
Discodoris heathi MacFarland, 1905
3.
DENDRODORIDIDAE
Doriopsilla albopunctata (Cooper, 1863)
Ale
Dendronotacea
The Veliger, Vol. 26, No. 3
TRITONIIDAE
Tritonia diomedea Bergh, 1894
6(s).
Tritonia festiva (Stearns, 1873)
1-2, 3, 4, 16, 21. In Humboldt County, 772tonia festiva
exhibits two distinct coloration patterns. The dominant
phase consists of the typical white ground color with a
dorsal, reticulating, opaque white line network; a series
of middorsal, oval pink spots is present on some individ-
uals. Specimens collected at the HBCGS (#16) exhibited
the alternate coloration, a translucent light pink ground
color with little or no evidence of a dorsal, white line
network. At this study site, a population of the pink al-
cyonacean octocoral Gersemia rubiformis (Pallas, 1788) ex-
ists and 7. festwwa preys on this anthozoan. The pink col-
oration of Tritonia does not appear to be restricted to the
digestive tract as reported by GOMEZ (1973) for specimens
of T. festiva feeding on Lophogorgia chilensis (Verrill, 1868).
The feeding behavior differs from previously published
accounts of tritonid feeding (GOMEZ, 1973; THOMPSON,
1976a). When Tritonia comes in contact with a Gersemia
colony, the predator’s oral veil expands laterally and the
specimen lunges into the alcyonacean colony. The pink
anthozoan tissue can be observed passing through the buc-
cal mass into the esophagus. The calcareous spicules of
Gersemia are present in the fecal pellets of pink specimens
of Tritonia.
The utilization of Gersemia rubiformis as a prey item
by T. festiva contradicts NYBAKKEN & MACDONALD (1981)
who state “the unusually narrow radula of T. festiva seems
to correlate with the prey” (in that case Clavularia sp.).
Tochuina tetraquetra (Pallas, 1788)
6, 6(s).
HANCOCKIIDAE
Hancockia californica MacFarland, 1923*
6. This species was found exclusively on the rhodophyte
Polyneura sp. attached to wharf pilings at this study site.
The sighting of Hancockia californica in Humboldt
County represents a geographical range extension. The
previous northernmost occurrence of H. californica was
Dillon Beach, Marin County, California (MCDONALD &
NYBAKKEN, 1980).
DENDRONOTIDAE
Dendronotus diversicolor Robilliard, 1970
6.
Dendronotus frondosus (Ascanius, 1774)
1-2, 3, 4, 6, 6(s), 12, 13, 16, 17, 18, 22-23.
Dendronotus iris Cooper, 1863
15),
Dendronotus subramosus MacFarland, 1966
3, 4, 6, 16. Observed feeding on the hydroids Obelia sp.
and Tubularia marina (Torrey, 1902).
W. J. Jaeckle, 1984
Page 211
Table 2
Hydrozoan prey species of Hermissenda crassicornis.
Anthomedusae
Eudendrium californicum
Eudendrium rameum (Linnaeus, 1758)
Stauridiosarsia japonica (Nagao, 1962)
Tubularia crocea
Tubularia marina
Polyorchis sp.
DOTIDAE
Doto amyra Marcus, 1961
1-2, 6. Although no specimens definitely assignable to
Doto amyra were sighted during this study, BoyD &
DEMarTINI (1977) and BoypD (1979) have reported this
species from Humboldt County.
Doto columbiana O’ Donoghue, 1921
12. Feeding on Obelia sp.
Doto kya Marcus, 1961
3, 4, 12, 16. ROLLER’s (1970a) and MCDONALD’s (1975,
1977) work on the five species of Doto described by
Marcus (1961) and MACFARLAND (1966) resulted in the
three currently recognized species of this genus in the
northeast Pacific: Doto amyra, D. columbiana, and D. kya.
However, MCDONALD (1977) commented on the contin-
ued taxonomic confusion surrounding these five species,
and BEEMAN & WILLIAMS (1980) reported on the diffi-
culty of species identification. Specimens have been col-
lected in Humboldt County which are morphologically
identical to Marcus’ (1961) description of D. amyra, but
the presence and distribution of black pigmentation on the
cerata and dorsum indicate that these specimens are rep-
resentatives of D. kya. Systematic revision is clearly need-
ed.
Doto kya possesses a varied diet, utilizing Abzetinaria
sp., Aglaophema struthionides (Murray, 1860), Euden-
drium californicum, Obelia dichotoma (Linnaeus, 1758),
Plumularia sp., and Sertularella sp. as prey. Nidosomes of
Doto spp. have been found throughout the year in the
hydrorhizal area of all species, except E. californicum.
Arminacea
ARMINIDAE
Armina californica (Cooper, 1863)
4. Although typically found on sandy mud bottoms
(McDONALD & NYBAKKEN, 1980) in association with Re-
nila spp. and Ptilosarcus gurney: (Gray, 1860) (Mac-
FARLAND, 1966; MCDONALD, 1977), the single specimen
collected in Humboldt County was found in a rocky lit-
toral habitat with no evidence of pennatulacean prey
species in the area of collection.
Leptomedusae
Abietinaria abietina (Linnaeus, 1758)
Abietinaria greene: (Murray, 1860)
Campanulana ritterr Nutting, 1901
Halecium corrugatum Nutting, 1899
Obelia dichotoma
Sertularella conica Allman, 1877
Chondrophora
Velella velellaLinnaeus, 1758
This specimen’s coloration deviated significantly from
normal pigmentation patterns described for Armuina calt-
fornica. The dorsum was completely white with no evi-
dence of light pinkish-brown or cream pigmentation.
DIRONIDAE
Dirona albolineata MacFarland in Cockerell & Eliot, 1905
1-2, 4, 6, 6(s), 14, 16, 22-23.
Dirona picta MacFarland in Cockerell & Eliot, 1905
12, 3 4 6, 14h, 6, ZA=22)-
JANOLIDAE
Janolus fuscus O’ Donoghue, 1924
3, 4, 6, 13, 16, 22-23.
Aeolidacea
FLABELLINIDAE
Flabellina iodinea (Cooper, 1863)
6(s).
Flabellina price: (MacFarland, 1966)
1-2, 6. No specimens of this species were sighted during
this study; however, BoyD & DEMarTINI (1977) and
BoypD (1979) reported Flabellina price: from Humboldt
County.
Flabellina trilineata (O’Donoghue, 1921)
1=2, 4, 5, G5 WD; 16s
EUBRANCHIDAE
Cumanotus beaumonti (Eliot, 1906)
17. When disturbed, the cerata of the examined speci-
men moved in a coordinated dorso-ventral fashion;
THOMPSON (1976b) depicts this defensive swimming be-
havior.
Eubranchus rustyus (Marcus, 1961)
3, 4, 6, 12, 16.
TERGIPEDIDAE
Cuthona abronia (MacFarland, 1966)
4.
Cuthona albocrusta (MacFarland, 1966)
3. A 6, 13:
Page 212
The Veliger, Vol. 26, No. 3
Cuthona cocoachroma Williams & Gosliner, 1979
6, 16.
Cuthona columbiana (O’Donoghue, 1922)
3, 6:
Cuthona divae (Marcus, 1961)
3, 4, 6, 16. In Humboldt County, this species is in-
variably found in close association with its food source
Hydractinia milleri Torrey, 1902 (McDONALD &
NYBAKKEN, 1980). Numerous pink nidosomes have been
found on the perisare of H. milleri, presumably deposited
by adjacent specimens of C. divae. The deep pink ceratal
coloration of these specimens is probably attributable to
ingested 7. miller: polyps.
Cuthona flavovulta (MacFarland, 1966)
3, 4, 6.
Cuthona lagunae (O’Donoghue, 1926)
3, A. 6,
FACELINIDAE
Hermissenda crassicornis (Eschscholtz, 1831)
12, 3, 4, © GO), & 12, 13, 14, 16, 17, Ue, A223, Iho
terms of abundance and geographical distribution, Her-
missenda crassicornis is the dominant littoral opistho-
branch in Humboldt County. During this study, H. cras-
stcornis has been observed feeding on numerous hydrozoan
species (Table 2).
AEOLIDIIDAE
Aeolidia papillosa (Linnaeus, 1761)
Nea, BS, 4 GO, 12, 4 MG, ZO.
ACKNOWLEDGMENTS
Special thanks are extended to Drs. David Behrens, Gary
Brusca, and Terrence Gosliner for critically evaluating
this work prior to manuscript submission. I also would
like to thank Tim Stebbins and Cathy Smith for supplying
data on Alderia modesta and Hancockia californica, Kirsten
Rohrbach, Michele Levin and Priscilla Mepyans for ac-
companying me on numerous collecting trips, Dorothy
Soule for identifying Lyrula hippocrepis, and Mrs. Ruth
Toyama for typing the manuscript. This paper is contri-
bution number 401 to the Allan Hancock Foundation.
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Page 213
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Ro.ier, R. A. & S. J. Lonc. 1969. An annotated list of the
nudibranchs from San Luis Obispo County, California. Ve-
liger 11:424-430.
SpHon, G. G. & J. R. Lance. 1968. An annotated list of
nudibranchs and their allies from Santa Barbara County,
California. Proc. Calif. Acad. Sci., 4th series 36:73-84.
TuHompson, T. E. 1976a. The biology of opisthobranch mol-
luscs. Vol. 1. Roy. Soc. London. 207 pp.
THompsoNn, T. E. 1976b. Nudibranchs. T. F. H. Publications,
Inc. Ltd., Neptune City, New Jersey and Reigate, Surrey,
England. 96 pp.
WiIcKSTEN, M. K. & J. D. DEMarTINI. 1973. Observations
of the feeding habits of Tochuina tetraquetra (Pallas) (Gas-
tropoda: Tritoniidae). Veliger 15:195.
The Veliger 26(3):214-228 (January 3, 1984)
THE VELIGER
© CMS, Inc., 1984
Doridacean Nudibranchs from Sri Lanka, with
Descriptions of Four New Species
NATHALIE YONOW'!
Department of Zoology, University of Bristol, England
and University College of Swansea, Wales
Abstract. Eight doridacean nudibranchs from northeastern Sri Lanka are described and illustrated.
Of these, two chromodorids, Chromodoris conchyliata and C. adeima, are new species. Two of the
three phyllidiids found also are new to science, Phyllidia empelia and P. alia. The third, P. varicosa,
as well as Gymnodoris citrina are new records for Sri Lanka.
INTRODUCTION
THE MAJORITY OF observations on the opisthobranch mol-
lusks of the Indian Ocean have been concentrated along
the east coast of Africa: EDMUNDS (1971) described the
Doridacea from Tanzania and sixteen opisthobranch mol-
lusks from the Seychelles, Tanzania, and the Congo
(EDMUNDS, 1972). Rudman worked from eastern Africa
across to the tropical West Pacific (RUDMAN, 1977), as
well as in the Indo-West Pacific (RUDMAN, 1973, 1982).
The Red Sea has furnished a number of scientific collec-
tions: one of the first was ELIoT’s (1908) collection near
Sudan. Marcus & Marcus (1959) reported on the Red
Sea and the Maldives. GOHAR & ABUL-ELA (1959) stud-
ied the development of three Red Sea nudibranchs, and
more recently SOLIMAN (1978, 1980) has been working
on the biology of Red Sea dorids.
The first records of opisthobranch mollusks from Sri
Lanka were published by KELAART (1858, 1859) and were
based on collections made in the vicinity of Trincomalee.
Walter Elliot collected along the northwestern coast of
India during the period 1853-54, accompanying his col-
lection of 41 species with accurate drawings. He sent his
drawings and preserved specimens to ALDER & HANCOCK
in England, who published their studies in 1864. C. N.
E. EL1or (1906) reviewed these early finds, in addition to
FARRAN’s (1905) work and BERGH’s (1905) extensive col-
lections. Work on Indian and Ceylonese opisthobranchs
was thereafter sporadic: ELIoT (1909) added further de-
tails of fresh specimens to his previous work on Kelaart’s
animals; O? DONOGHUE (1932) made notes on 18 species
of nudibranchs and ascoglossans from the Gulf of Ma-
' Present address: Department of Zoology, University College
of Swansea, Swansea SA2 8PP, Wales.
naar; WINCKWORTH (1946) wrote on five species of chro-
modorids he found in Bombay. More recently, BURN
(1970) has drawn attention to the Phyllidiidae in redes-
cribing the rare Phyllidia zeylanica, rediscovered after al-
most 100 years in the Gulf of Kutch, western India.
The opportunity arose while visiting Sri Lanka during
the summer of 1981 to initiate a new investigation into
the opisthobranch Mollusca and their habitats in the re-
gion of Trincomalee, the site of Kelaart’s first collection
of opisthobranchs in Ceylon.
Sri Lanka is a large island, approximately 65,600 km?
in area, situated in the Indian Ocean southeast of Cape
Cormorin in India. The city of Trincomalee is located on
the northeastern coast, which is characterized by sandy
bays enclosed within rocky outcrops, with some well-de-
veloped lagoon areas and a few coral islands and bays.
This coast is exposed to strong winds during four months
of the year, with maxima in January (U.S. Navy, 1957).
In this investigation, 14 species of opisthobranchs were
found, 8 of which belong to the suborder Doridacea. Four
are described as new species, two Chromodorididae and
two Phyllidiidae. Of the remaining four, two are new
records for Sri Lanka, Gymnodoris citrina and Phyllidia
varicosa. Gymnodoris citrina is redescribed and the problem
of discriminating between G. bicolor and G. citrina is dis-
cussed. New observations are presented on the anatomy
and histology of several species.
COLLECTION anp METHODS
All the specimens were collected from three localities north
of Trincomalee in relatively shallow water (1-4.5 m):
none of the reefs is exposed at low tide. Descriptions,
drawings, and color photographs of external features were
made from life. Anatomical investigations were made us-
ing specimens relaxed in 7% magnesium chloride, pre-
N. Yonow, 1984
Page 215
Figure 1
Gymnodoris citrina A. dorsal aspect; B. side view of the rhinophore; C. penal spines (with aid of camera lucida);
D. radular teeth (with aid of camera lucida).
served in 4% formalin, and later transferred into 70%
alcohol. Jaw and radula preparations were made by re-
moving the buccal mass, dispersing the flesh in warm
caustic soda (NaOH), and mounting in polyvinyl lacto-
phenol with lignin pink. The reproductive organs of the
single specimens were not dissected in order to preserve
the type specimens as completely as possible after remov-
ing the radula.
Holotypes and paratypes of the new species have been
lodged in the British Museum (Natural History).
Gymmnodoris citrina (Bergh, 1877)
(Figure 1)
Trevelyana citrina BERGH, 1877
Gymnodoris citrina: YOUNG, 1967
Page 216
The Veliger, Vol. 26, No. 3
Material and locality: One specimen, collected under a
rock at a depth of 2 m off Pigeon Island (northeast of
Trincomalee), on 26 August 1981.
Description: The specimen was 28 mm long and approx-
imately 5 mm wide. It is milky white with small, orange-
yellow, low-pointed papillae scattered over the dorsal sur-
face. It is not bilaterally symmetrical; the enlarged genital
papilla (now a tube in the preserved specimen) is located
to the right of the midline, anterior to the gills, and the
branchiae are to the left of the median. Two rows of
orange-yellow pointed papillae form a slightly asymmet-
rical V-shaped pattern on either side of the branchiae.
The dorsal surface of the tail and the genital papilla are
free of papillae. The front of the mantle is broadly round-
ed and bears 14 pointed orange-yellow projections (Figure
1A).
The bulbous rhinophores are darker than the pallial
tubercles and distinctive in shape. They each have a thin
stalk, 15 vertical lamellae, and a swollen club at the distal
end (Figure 1B). The branchiae are 9 in number, set in
a crescent shape anterior to the small anal papilla. In life,
the gills were translucent white, and retracted after much
stimulation.
The radula is broad, with the formula 20 x 28-0-28.
There is no median tooth, but the cuticle contains a faintly
reticulate substructure. The number of marginals in-
creases towards the growing end. The first marginal tooth
is more than twice the size of the second marginal: the
largest first marginal measures approximately 300 um in
length. Each of these large teeth has a long, narrow root
and a long, curved, pointed cusp. Root size in proportion
to the cusp diminishes towards the outer edges of the rad-
ula. The outermost marginals exhibit abruptly recurved
tips (Figure 1D). No recognizable jaws survived caustic
treatment.
A squash preparation of the retracted penis shows that
there are spines lining the lumen. They take the form of
triangular arrowheads, approximately 6.6 um long (Fig-
ure 1C).
Remarks: Two similar species of Gymnodoris exist and
have posed difficulties in identification. Gymnodoris bicolor
(Alder & Hancock, 1864) and G. citrina (Bergh, 1877)
have been differentiated by the size of the first marginal
tooth relative to body size, by the shape of the second
marginal, and by the size difference between the first and
second marginals. In G. bicolor, the first marginal tooth is
small in relation to body length; the shape of the second
marginal is elongated and triangular; and the second mar-
ginal is only slightly smaller than the first marginal. In
G. citrina, the first marginal is large relative to body length;
the second marginal has an awl-shaped cusp and a broad
base; and the second marginal is very much smaller than
the first, less than half the size. In my specimen, the ratio
between body length and first lateral is intermediate, and
the first marginal is more than twice the size of the second
marginal.
Other, less ambiguous, characteristics follow. The lo-
cation of the genital opening relative to the gills differs in
both species: in G. bicolor, the aperture is posterior (KAY
& YOUNG, 1969) and in G. citrina anterior (YOUNG, 1967)
to the gills. The cirral hooks of G. bicolor are 24-36 um
long (Kay & YOUNG, 1969) whereas in G. citrina they are
an order of magnitude smaller, 7-8.5 wm (YOUNG, 1967).
In my specimen they were approximately 6.6 um long.
The V-shaped arrangement of papillae on the dorsum also
seems to be characteristic of G. citrina.
Distributions of G. bicolor and G. citrina are uncertain
because ambiguous radular descriptions and incomplete
morphological descriptions have not been sufficient to en-
able one to distinghish between the two. Certain identi-
fications of G. cztrina indicate a western Indo-Pacific dis-
tribution: Palau Island (BERGH, 1877), Eniwetok Atoll
(YOUNG, 1967), and now Sri Lanka.
Chromodoris conchyliata Yonow, spec. nov.
(Figures 2 and 9A, B, C)
Material and locality: One specimen found under dead
coral at a depth of 4 m in Koduwakattumalai Bay (35 km
north of Trincomalee), on 7 August 1981.
Holotype: BM(NH) 19837 W.
Description: The animal was 15 mm long, with the foot
extending beyond the mantle. The anterior and posterior
ends of the mantle and the rear of the foot are edged with
a milky white band. The anterior part of the mantle is
bilobed. The body is pale violet with rounded areas of
creamy yellow, and deeper violet and red markings. There
are 3 dark violet markings on the dorsum: a V-shape near
the front with the ends pointing towards the rhinophores,
2 broad lateral bands converging in the midline anterior
to the gills, and an X-shape on the rear of the mantle.
These dark violet marks redden in places and follow the
contours of bilaterally symmetrical yellow spots (Figure
2A). Ventrally, the head, the simple oral tentacles, and
the foot are white. The hyponotum is dark purple in the
region that corresponds to the pale violet on the dorsum.
Where the edging is white above, it is bright red ventrally,
fading into white near the head (Figure 2B).
In lateral view, a longitudinal dark violet line can be
seen between the foot and the mantle. The animal is fairly
high when observed from this angle (Figure 2D).
The rhinophores are lamellated, colored red with white
stalks, and retractile into sheaths (Figure 2C). The gills,
8 simple pinnate structures, are tricolored: the upper half
is red, both rachis and pinnae, and the lower half has a
pale violet rachis with white pinnae (Figure 2E).
The radular formula of the specimen is 43 x 33-1-33.
The median tooth is vestigial. All the teeth have pointed
denticulations, and the first tooth on either side of the
median has a subsidiary cusp (Figures 2F and 9A). The
jaw plates consist of blunt hooked rods, the largest about
2 um long.
N. Yonow, 1984
Page 217
L 2") red
red violet
(| creamy yellow
| pale violet
30
yy
Figure 2
Chromodoris conchyliata Yonow, spec. nov. A. dorsal aspect; B. ventral view of the head; C. side view of the
rhinophore; D. lateral view; E. gill; F. radular teeth (with aid of camera lucida).
Remarks: This species is distinct from all previously de-
scribed chromodorids in its color pattern, with 3 distinct
sets of dark violet markings on a pale violet body color
and the bilobed anterior margin, not a common feature in
chromodorids. This species is distinguishable from Chro-
modoris geometrica Risbec, 1928, similarly patterned with
violet markings. Chromodoris geometrica has rays of purple
radiating from two parallel median bands (also purple);
the rhinophores have white stalks with yellow lamellae;
the branchiae are seven in number, each with a yellow
Page 218
The Veliger, Vol. 26, No. 3
red
yellow
white
Figure 3
Chromodoris adeima Yonow, spec. nov. A. dorsal aspect; B. ventral view of the head; C. side view of the rhinophore;
D. radular teeth (with aid of camera lucida).
rachis and transparent white pinnae (YOUNG, 1967).
Chromodoris geometrica seems to be limited to the eastern
Pacific: New Caledonia (RISBEC, 1928, 1953), New South
Wales (ALLAN, 1947) and Eniwetock Atoll (YOUNG, 1967).
The radular formulae are similar, as is the form of the
teeth. The radula of a 22 mm-long specimen of C. geo-
metrica is 43 X 28-0-28; the teeth are 53-79 um long and
denticulate. The jaw plates consist of simple bifid hooks
32-39 wm long (YOUNG, 1967). RUDMAN (1973) also de-
scribes C. cf. geometrica, a chromodorid with purple retic-
ulations. He states that the color is somewhat variable if
the records from New Caledonia, Australia, Eniwetok,
N. Yonow, 1984
Page 219
“cusp Y
Figure 4
Kentrodoris rubescens A. radular teeth (with aid of camera lucida); B. vestibular stylet (with aid of camera lucida).
and Kenya are of the same species, but that the specimens
are linked by (1) the orange-yellow rhinophores (mine
were red) and gills (mine were pale violet and white with
red), (2) the purple reticulate pattern, and (3) the white
yellow pustules. The described specimen probably belongs
to the same color group as the above, but is certainly a
separate species.
The name conchyliata is derived from the Latin con-
chyliatus, meaning “‘dressed in purple.”
Chromodoris adeima Yonow, spec. nov.
(Figures 3 and 9D, E, F)
Material and locality: One specimen, found in coral rub-
ble 2.5 m deep, 15 km north of Trincomalee, on 11 August
1981.
Holotype: BM(NH) 19838 W.
Description: This was a fleshy animal, 20 mm long and
10 mm wide. The crenulate mantle completely covered
the foot when the animal was crawling. The body is faint-
ly papillate, but soft and strikingly marked. The dorsum
is red with faint patches of mottled yellow and red. Along
the edge of the mantle is a poorly defined line of red dots,
some running together, outside of which is a creamy yel-
low band. External to the yellow is a vivid green band
edging the upper and lower surfaces (Figure 3A). The
foot, also fleshy and crenulated, has similar colorings to
the mantle: it is a lighter shade of red edged with yellow
and green. The foot is notched and bilabiate. The head
and the simple oral tentacles are green (Figure 3B).
The rhinophores are unusually close to the end of the
mantle, and retract into prominent sheaths. A rhinophore
bears 23 lamellae, although the last 6 do not go all the
way around the organ. The stalk is very short. The color
Page 220
The Veliger; Vols 26Noms
Figure 5
Platydoris scabra A. dorsal aspect of small specimen (semi-diagrammatic) drawn from preserved specimen; B. detail
of dorsal pigment; C. penis (reconstruction), a = vas deferens, b = cuticularized penis, c = muscular body wall, d =
accessory gland; D. radular teeth of larger specimen (with aid of camera lucida).
pattern on the rhinophore is interesting: the whole is
sheathed in red, and underlying this layer is a green pig-
ment which decreases in area towards the base, where the
sides and back of the rhinophore are red and the anterior
surface is green. The midline, where the lamellae stop just
short of meeting each other, is white for the entire length
of the rhinophore (Figure 3C).
There are 19 fleshy gills, which retract into a large
cavity with a raised edge. The outer ring consists of 11
larger gills, inside which are 8 smaller gills. They are
N. Yonow, 1984
Page 221
brightly colored, a red rachis with red pinnae at the base,
green in the center, and white at the tip. When fully
extended, the gills project beyond the mantle edge on both
sides and at the posterior end.
The radular formula for the specimen is 38-1-38. The
number of rows differs on the two sides: 109 and 116.
The median tooth is triangular and the rest of the teeth
vary in form and size along the row. By the third tooth,
the cusp is long and, toward the new end of the radula,
sharp. The knob at the juncture of the cusp and root
diminishes as the teeth grow older, as does the length of
the cusp. All the teeth in each row are denticulate, with
7-8 denticulations present only on one side (Figure 3D
and 9D, E, F). The jaw plates are made of crescent-
shaped, smoothly tapering rods, averaging 5 um in length.
Remarks: A number of Chromodorididae have a dorsal
pattern similar to Chromodoris adevma, but the colors dif-
fer. Casella atromarginata (Cuvier, 1804) can be green with
a white and black margin. Chromodoris splendida (Angas,
1864) is cream with red markings and a bright yellow-
orange pallial edge. Chromodoris preciosa (Kelaart, 1859)
is a white animal with a red border and yellow sub-mar-
gin. The colors of C. adeima as well as its radula are
enough for it to be considered a distinct species.
In Greek, adeimos is one of the many words meaning
‘“‘brave, bold and fearless.”
Kentrodoris rubescens Bergh, 1876
(Figure 4)
Kentrodoris rubescens BERGH, 1876
Marcus, 1976
Material and locality: One specimen found under a rock
with much epiphytic growth 2 m deep, 15 km north of
Trincomalee, on 31 July 1981.
Description: The live animal was 90 mm long and 25
mm wide. The specimen was soft, smooth, and slimy. The
base color is beige with red-brown longitudinal linear
markings. Yellow-green areas are present between some
sets of lines. The lines are not continuous, nor of uniform
thickness, so there are regions of beige devoid of lines as
well as patches of red-brown where the beige is barely
visible. The highest concentrations of dark pigment are
found at the anterior and posterior ends, where the linear
markings are shorter and thicker. The darker patches tra-
verse the dorsum. The foot is concealed by the notum and
is beige, with wavy linear markings, and the hyponotum
extending beyond the foot is white. The dorsum is highest
in the region of the branchiae, which are located slightly
posterior to the mid-dorsum. There is a high sheath pro-
tecting a deep cavity into which a circlet of 7 gills is re-
tracted. The gills when fully extended stand approxi-
mately 2 cm above the notum. They are bicolored: the
proximal half is white and the distal red-brown. The rachis
is white with branching pinnae.
The gill sheath is darker, because of converging and
thickening lines, as are the prominent rhinophore sheaths.
The lamellated rhinophores are almost 15 mm in length,
with brown bases and white tips.
The radular formula is approximately 35 x 25:0-25.
All the teeth are squared except for the last one, which is
rounded. The first lateral is distinctly different from the
others: the root is stronger and wider, more square than
rectangular. The first 7-8 teeth of each row have a groove
along the inner surface of the cusp, not present in the
other teeth. The end tooth in each row differs from the
others in having a very rounded end, noticeable among
the squared, blunt ends. The root of this last tooth is small
and not very strong (Figure 4A). The jaw plate was caus-
tic resistant, with no recognizable substructure.
The vestibular stylet is 7.5 mm long, chitinous, and
enclosed in a membrane (Figure 4B).
Platydoris scabra (Cuvier, 1804)
(Figure 5)
Doris scabra CUVIER, 1804a
Platydoris scabra: Marcus & Marcus, 1959
EDMUNDs, 1971
SOLIMAN, 1978
Material and locality: Two specimens found in 2-3 m,
15 km north of Trincomalee, on 11-12 August 1981.
Description: The smaller specimen was 20 mm long and
15 mm wide, the body oval and flattened. It is granular,
tough, and leathery to the touch. The dorsal side of the
animal is creamy yellow, almost pale orange, with brown
patches and speckles. The patches are paired and nearly
symmetrical: 2 small patches anterior to the rhinophores
and 2 larger patches just posterior to the rhinophores, in
contact with the rhinophoral sheaths. The crescent-shaped
patches are larger, meeting in the center and pointing
toward the gill pocket. Two patches are located anteriorly
in the crescent hollows and make the pattern transversely
linear again. Posterior to the branchiae are 3 small patches
arranged in a semi-circle around the pocket. Around the
periphery are discontinuous lighter patches. A number of
small spots are scattered among the large patches and
around the edge (Figure 5A). The variations in color are
caused by the presence and absence of small brown dots,
which converge in regions of dark color (Figure 5B).
The ventral side of the mantle is creamy, devoid of
pigment. The foot, although not pigmented, is darker than
the hyponotum. It does not project beyond the mantle.
The sides of the foot are finely speckled with brown dots
which increase in concentration to form a line in the re-
gion between the dorsal surface of the foot and the hy-
ponotum. This line is not visible from underneath when
the animal is crawling.
The pallial edge is orange, visible only in lateral view.
The rhinophores are lamellated and retract into promi-
nent sheaths 1.3 mm across. The sheaths have a smooth
Page 222 The Veliger, Vol. 26, No. 3
Figure 6
Phyllidia empelia Yonow, spec. nov., drawn from preserved specimen (holotype): A. dorsal aspect; B. ventral view
of the head. Phyllidia alia Yonow, spec. nov., drawn from preserved specimen (holotype): C. dorsal aspect; D.
ventral view of the head.
rim and are creamy in color, with a few faint radiating is star-shaped with a smooth rim, symmetrical on either
brown lines. side of the median. Like the rhinophoral sheaths, it ex-
The 6 large gills are voluminous pinnate structures, hibits the base color with even fewer markings on the
contractile into a single cavity. The crenulated gill pocket outside edge; the inside is creamy.
N. Yonow, 1984
The radular formula is 43 x 99-0-99, and the radula
is 4.5 mm long and 3 mm wide. The teeth are long hooks,
approximately 16 wm long, with relatively small roots.
The first tooth, however, has a long rounded root and
short cusp, but the second tooth in the first 16 rows has
the typical pointed cusp. The second and subsequent teeth
onwards of row 16 are twisted. The last few teeth in each
row degenerate rapidly into blunt, rounded, irregular
structures.
The penis was sectioned to look for spines and a recon-
struction has been drawn (Figure 5C). The penis is re-
tracted and the spines line the lumen, which is cuticular-
ized. The spines are large boss-like structures with a small
curved spine at the end, the largest measuring 450 um
high and 375 um wide.
No description is available from life for the second spec-
imen. In alcohol it measures 39 mm in length and is 34
mm wide. The dorsal pattern is preserved and will be
described. This pattern differs from the previous specimen
and from other Platydoris scabra. There is a dorsal round-
ed triangular shape very lightly pigmented, and the region
surrounding it is dark. The brown pigment is in the form
of dots identical to the smaller specimen. The pallial edges
are crenulate, each indentation showing an increase of
brown pigment. The area behind the gill is darkly pig-
mented, and the area anterior to the rhinophores is some-
what lighter. The ventral side is exactly as described for
the first specimen, with a long (23 mm) narrow foot. The
pigmented region between the foot and the mantle is 10
mm wide.
The rhinophore sheaths are 2 mm in diameter and the
gill pocket 5 mm across.
The radular formula is 36 X 66-0-66. The teeth are
smaller than those of the first specimen, the largest with
a cusp 100.56 um long. The teeth are as for specimen 1,
the first tooth with a shorter cusp than the following teeth.
The twisting-over occurs further along the row at the
growing end: in row 15 the twisting is visible in the sixth
tooth, but from row 19 onwards, the second tooth is twist-
ed (Figure 5D). No recognizable substructure of the jaw
plates survived caustic treatment.
Phyllidia empelia Yonow, spec. nov.
(Figures 6A, B, 7A, 8A, B)
Material and locality: Two specimens found on the sides
of large rocks, 2 and 4.5 m deep, in Koduwakattumalai
Bay, on 7 and 12 August 1981.
Holotype: BM(NH) 19839 W/1.
Paratype: BM(NH) 19839 W/2.
Description: The smaller specimen (holotype) is 20 mm
long and 7.3 mm wide in alcohol. The oval body is elon-
gate, completely concealing the foot. The base color is
black, and the tubercles are gray. The animal is softer
and more flexible than the other species of Phyllidia found
Page 223
in Sri Lanka. The gray oral tentacles are squarish and
joined together at the base. The foot is also gray, without
a median line (Figure 6B).
The dorsal pattern is conveniently described from the
pallial margin to the midline. A thin gray band without
tubercles encircles the animal. Inside this is a thin black
stripe (just visible in places on Figure 8B). Also forming
a complete oval is the first row of tiny tubercles: these are
gray and single, and the gray region around the bases
merges into a continuous gray band. Inside this is a flat
black band, followed by another row of tubercles. These
are larger, 1 mm across, and multi-tuberculate, with a
maximum of 3 tubercles. This row has 2 indentations in
the oval, near the center at the widest point of the animal,
corresponding with 3 tri-tuberculate lumps. The next black
band is adjacent to and external to the rhinophores. Inside
this black band the tubercles emerge with some regularity.
A ring of 6 tubercles is found anterior to the rhinophores,
and another ring is found posterior to the anus. The me-
dian tubercles then alternate between both sides and the
center, some single and some compound. There are 9 tu-
bercles down the center, rounded towards the anterior and
posterior ends, and elongated in the middle (Figure 6A).
The rhinophores and anus are just inside the third black
stripe. The black rhinophores are lamellated and large in
comparison to other Phyllidiidae; the sheaths are gray.
The anus is a small slightly raised gray tube exactly on
the midline.
The larger specimen (paratype) is 26 mm by 10 mm
in alcohol. It conforms to the above color description, but
proportions vary slightly. The first gray and black lines
of the margin are very fine, scarcely visible. The first row
of tubercles is as described, but the tubercles in the second
row are elongated transversely, forming a ring of perpen-
dicular ridges around the edge. The four posterior tuber-
cles merge with the outer row of single tubercles and the
fine gray line that surrounds the whole. The median tu-
bercles have the same patterns described above but there
are 10 tubercles down the center (Figure 8A).
The foot is gray, lacking a median line, and is marked
transversely with two black slashes; one crosses the foot
and the other crosses over just half the foot. The oral
tentacles are as previously described.
The long, pointed rhinophores are sheathed and la-
mellate. Unlike most nudibranch rhinophores, the 16 la-
mellae in this species are very short; they do not grow
diagonally across the length of the rhinophore and they
overlap each other from the base to the tip. Only at the
distal tip do the lamellae actually meet in the dorsal and
ventral midline of the rhinophore. The subsequent 11 la-
mellae stop short of the base, the last 6 running perpen-
dicular to it. The rhinophore of this second specimen has
a length of 2 mm (Figure 7B).
Remarks: This species has a number of characteristics
that serve to distinguish it from other Indo-Pacific and
Pacific Phyllidiidae. It seems similar to Phyllidia nobilis
Page 224
The Veliger, Vol. 26, No. 3
Figure 7
Rhinophores: A. Phyllidia alia Yonow, spec. nov., drawn from preserved specimen (holotype); B. P. empelia
Yonow, spec. nov., drawn from preserved specimen (paratype); C. P. varicosa, drawn from preserved specimen.
Bergh, 1869, as described by EDMUNDs (1972), ELIOT
(1904a), and RisBEc (1953). However, both Sri Lankan
specimens were gray and black, with no trace of orange
or green as recorded by these authors. My two specimens
show some variation in size and shape of the tubercles,
but follow the same sequence of pattern: two uninter-
rupted rows of gray tubercles surround the whole dorsum,
plus one that is broken on each side but continuous around
both ends. Phyllidia albonigra Quoy & Gaimard, 1832,
from Tonga vaguely resembles Phyllidia empelia, but the
anterior and posterior extremities of the Tongan species
are pointed, and the compound tubercles are not arranged
in any definite pattern. Phyllidia zeylanica Kelaart, 1859,
is similar in pattern to P. empelia, but P. zeylanica has
pink tubercles and pink and black rhinophores. On my
specimens, the rhinophores are completely black, and no-
ticeably large, a fact not mentioned by previous authors.
Because of the lack of color in this species, I have called
it empelia from the Greek empelios, meaning “gray.”
Phyllidia alia Yonow, spec. nov.
(Figures 6C, D, 7A, 8F, G)
Material and locality: Two specimens found 1 m and 4
m deep, respectively, on the sides of rocks in Koduwakat-
tumalai Bay, on 3 and 7 August 1981.
Holotype: BM(NH) 198310 W/1.
Paratype: BM(NH) 198310 W/2.
Description: The first specimen (holotype) measures 22
mm by 8.5 mm in alcohol, oval and elongate, in conform-
ity with the majority of Phyllidiidae. In this specimen,
however, the body color is white with black lines and
yellow splashes on the tubercles. The white mantle edge
is flattened, with tiny blisters around it, and a few spots
of black. This white band is 2.5 mm wide, narrowing at
the anterior and posterior ends. At its inner margin is a
row of larger blisters, tipped with yellow. Two lines of
black pigment run down either side, beginning at a point
on the anterior edge of the mantle and ending posteriorly
on either side of the anus, which is located on a yellow
tubercle along the midline. These black regions are non-
tuberculate. Inside this is an ellipse of large simple, grainy
tubercles. The largest ones (whiter in the photograph,
Figure 8F) are bright yellow in color. The smaller white
tubercles have bases that tend to merge with one another.
The rhinophores are located on the anterior edge of this
ellipse and the anus at the posterior. The midline is a
black line which divides at the base of each of 3 large
yellow tubercles, running around them and meeting again
on the other side (Figure 6C).
The rhinophores are bright yellow, lamellated, and
Figure 8
A and B. P. empelia Yonow, spec. nov.; C, D and E. P. varicosa; F and G. P. alia Yonow, s
cm.
pec. nov. Scale = 1
Page 226 The Veliger, Vol. 26, No. 3
Figure 9
Scanning electron micrographs of chromodorid radulae. Scale = 10 um. Chromodoris conchyliata Yonow, spec. nov.:
A. midline of radula; B. center of radula; C. outer edge of radula. Chromodoris adeuma Yonow, spec. nov.: D.
midline of radula; E. center of radula; F. outer edge of radula.
N. Yonow, 1984
sheathed. The drawing (Figure 7A) is of a preserved spec-
imen: the rhinophores are short and squat, and the 14
lamellae run almost parallel to the sheath. They overlap
each other from distal to proximal, and the last 4 do not
meet at the midline. In the photographs of live material,
the rhinophores are slightly curved, finger-like projec-
tions, approximately 2 mm long. The gray oral tentacles
are bulbous with a rounded point on the inner edge, at-
tached separately to the head. Surrounding the foot on the
hyponotum, the gills are visible as short transverse black
lines, and the dorsal pattern of black shows through the
thin mantle (Figure 6D).
The second specimen (paratype) was larger, 30 mm
long and 12 mm wide in alcohol. The pattern is exactly
as for the first specimen, with 3 large tubercles down the
central black line. The anus, located on a tubercle in the
midline, can be clearly seen in the photograph (Figure
8G).
Remarks: This species was easy to establish as different
from other described Phyllidiidae. The pattern is striking
and almost exactly the same in both specimens. Phyllidia
alia resembles Phyllidia pustulosa Cuvier, 1804, but differs
in the thinness of its mantle edge, the lack of a regular
pattern in the tiny blisters interspersed with black mark-
ings around the edge, and the presence of two uninter-
rupted black lines on the dorsum. Phyllidia pustulosa is
said (PRUVOT-FOL, 1956) to have “tubercles on the pallial
edge sometimes grouped in triangular shapes, reminding
one of drawings of Phyllidia varicosa Lamarck, 1801, and
Phyllidia elegans Bergh, 1869. In general, in most of the
individuals figured, there are only vague irregular rows
on the edge of the mantle.” BABA & HAMATANI (1975)
describe P. pustulosa as slightly variable, but generally
with compound warts of 2-6 partially-united smaller
warts. The tubercles around the margin tend to be iso-
lated. CUVIER’s (1804b) drawing of P. pustulosa does not
resemble these specimens. PRUVOT-FOL (1956) has fur-
ther confused matters by misspelling P. pustulosa as P.
pustulata in the heading of her description. Neither she,
BABA & HAMATAMI, nor CUVIER refer to the two distinct
black lines on the dorsal surface, which serve to distin-
guish P. alia species from any other Phyllidia.
Alia is Latin, meaning “‘another.”
Phyllidia varicosa Lamarck, 1801
(Figure 7C, 8C, D, E)
Phyllidia varicosa LAMARCK, 1801
ELIoT, 1904b
EDMUNDs, 1972
BaBA & HAMATANI, 1975
P. trilineata CUVIER, 1804b
Quoy & GaAIMarRD, 1832
Material and locality: Three specimens found at depths
of 1 m and 4 m in Koduwakattumalai Bay, on 3 and 7
August 1981.
Page 227
Description: The specimens are oval in shape and hard
to the touch. All have the distinctive mark of Phyllidia
varicosa: an interrupted black line down the center of the
gray foot.
Specimen 1 measures 28 mm by 14 mm (22 mm x 10
mm in alcohol) and has the dorsal markings of a typical
P. varicosa. Two pairs of black lines run longitudinally,
with 3 ridges of yellow-tipped tubercles between them.
The tubercles have a grainy appearance. The central ridge
terminates with a knob containing the anus. The ridges
on either side begin just posterior to the rhinophores. The
edge of the mantle is more solid than in the other two
species and contains ridges of tubercles alternating with
solitary tubercles, surrounded by black. The first tubercle
of each transverse ridge is large and yellow. The solitary
tubercle is sometimes followed by a row of small tubercles
down to the mantle edge. Some of these second tubercles
are also yellow.
The yellow rhinophores are sheathed, finger-like pro-
jections with 14 lamellae running diagonally down the
organ. They start in a straight line at the distal end and
stop in a straight line just before the base, which makes
them conspicuous. The rhinophore is almost symmetrical
in lateral view, like a tall trapezoid with a narrow base
(Figure 7C).
Specimen 2 measures 55 mm by 25 mm in alcohol. The
markings are similar to specimen 1, but the 3 rows of
tubercles down the back cannot be described as ridges:
they are more like tubercles with their bases merging, less
delicate than the first specimen. These tubercles are or-
ange. The orange rhinophores are sheathed and lamellat-
ed, located as described above. The anus is present on the
last median tubercle.
Specimen 3, measuring 39 mm by 16 mm in alcohol, is
a more extreme form of specimen 2: the typical pattern is
still present, but more indistinct. The orange tubercles are
all much larger, elongated projections, different from the
grainy ridges of specimen 1. The first tubercles of the
transverse rows merge longitudinally, creating a discon-
tinuous third band of tubercles. The other details are as
described above.
ACKNOWLEDGMENTS
I should like to thank my parents, whose summer vacation
was spent looking for nudibranchs, and who supported
me while I was carrying out my research at the University
of Bristol. I am grateful to the University, and especially
to Dr. T. E. Thompson for his invaluable assistance and
encouragement, and for the use of his laboratory and ex-
cellent library. I thank Dr. Terrence Gosliner for his in-
terest and confirmation of the new species of chromodo-
rids, and Dr. M. R. Fordy for his help with the scanning
electron microscopy. Finally, I would like to express my
gratitude to my mother, Dr. P. J. Hayward, and Dr.
Thompson for their helpful criticisms of the manuscript.
Page 228
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BERGH, L.S. R. 1877. Malacologische Untersuchungen, 2. In:
C. Semper, Reisen im Archipel der Phillippinen, zweiter
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BerGH, L. S. R. 1905. Die Ophistobranchiata der Siboga-
Expedition. Siboga Exped. 50:1-248, 2 pl.
Burn, R. 1970. Phyllidia (Phyllidiella) zeylanica Kelaart, a rare
nudibranch from the Indian sub-continent. Mem. Nat. Mus.
Vic. 31:31-37.
Cuvier, G. 1804a. Mémoire sur le genre Doris. Ann. Mus.
Nat. Hist. Natur., Paris: 1-27.
Cuvier, G. 1804b. Mémoire sur la Phyllidie et sur le Pleuro-
branch, deux nouveaux genres de mollusques de l’ordre des
gastéropodes, et voisin des patelles et des oscabrions, dont
Pun est nu et dont l'autre porte une coquille cachée. Ann.
Mus. Natl. Hist. Natur., Paris 5:266-276.
EpDMuNDs, M. 1971. Opisthobranchiate Mollusca from Tan-
zania, III (Sub-order: Doridacea). J. Linn. Soc. (Zool.) 50:
339-396.
EpMuNbs, M. 1972. Opisthobranchiate Mollusca from the
Seychelles, Tanzania and the Congo, now in the Tervuren
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Euiot, C. N. E. 1904b. On some nudibranchs from East Af-
rica and Zanzibar, Part 6. Proc. Zool. Soc. Lond. 2:268-
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Eliot, C. N. E. 1906. On the nudibranchs of Southern India
and Ceylon, with special reference to the drawings by Ke-
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preserved in the Hancock Museum at Newcastle-upon-Tyne.
Proc. Zool. Soc. Lond. 2:636-691, 999-1008, pl. 42-47.
EvioT, C. N. E. 1908. Reports on the marine biology of the
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Eviot, C. N. E. 1909. Notes on a collection of nudibranchs
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The Veliger 26(3):229-232 (January 3, 1984)
THE VELIGER
© CMS, Inc., 1984
Technique for Narcotizing and Fixing Veliger
Larvae of Amphibola crenata
PENNY STIRLING,'! COLIN LITTLE,? MARGARET C. PILKINGTON
AND JOHN B. PILKINGTON
Department of Zoology and Portobello Marine Laboratory,
University of Otago, Dunedin, New Zealand
Abstract. A three-stage method for narcotizing veliger larvae is described, using calcium-free sea-
water followed by isotonic MgCl, and then a benzocaine-procaine mixture. Completely expanded
veligers of Amphibola can be prepared for scanning and transmission electron microscopy and light
microscopy.
INTRODUCTION
TO EXAMINE development of veliger larvae of the marine
pulmonate Amphibola crenata (Gmelin), we wished to fix
them with the velar lobes extended in the normal swim-
ming position. Initial tests using gradual additon of al-
cohol and isotonic (7.5%) MgCl, and bubbling CO,
through the seawater resulted in retraction of the velum
and closure of the operculum, either during the narcoti-
zation or upon addition of fixative. Use of chlorobutanol
as devised by BONAR & HADFIELD (1974) and subse-
quently employed by BICKELL & CHIA (1979) with nu-
dibranch veligers was successful with newly hatched Am-
phibola larvae, but even when used at low temperature it
caused older larvae to retract. The following three-stage
method was developed and resulted in successful fixation
for scanning electron microscopy (SEM), which required
a high success rate, for transmission electron microscopy
(TEM), and for 1 wm plastic sections for light microscopy
(LM).
TECHNIQUE anpD RESULTS
Veligers were raised from egg masses as described by PIL-
KINGTON & PILKINGTON (1982). They were placed in sea-
water in a solid watch glass and viewed under a dissecting
microscope. Sub-stage illumination was used, and this
produced a slight warming that seemed to aid the narco-
tization process. The following procedure applies to larvae
‘Permanent address: Department of Microbiology, Bristol
University, Bristol BS8 1TD, England.
? Permanent address: Department of Zoology, Bristol Univer-
sity, Bristol BS8 1UG, England.
in seawater, and appropriate dilutions must be made if
lower concentrations are used.
Stage I: Seawater was gradually replaced by calcium-free
seawater (with tonicity maintained by slightly increasing
magnesium concentration) (Table 1) over a period of about
10 min, using a Pasteur pipette. The intention was to
block synaptic transmission, as calcium-free salines have
been shown to do this in other molluscan systems (e.g.,
BERRY & PENTREATH, 1979). The treatment allowed the
larvae to continue swimming, but appeared to block the
normal retraction into the shell that is caused by chemical
or tactile stimulation.
Stage II: The calcium-free seawater was gradually re-
placed by isotonic MgCl,, and the larvae were left in this
for approximately 5 min while the final narcotizing so-
lution was prepared. Isotonic MgCl, is a well known nar-
cotic for marine invertebrates (e.g., GRIMSTONE & SKAER,
1972), but resulted in retraction into the shell if applied
before Stage I. The MgCl, solution slowed the swimming
rate of the larvae so that, although the cilia were still
beating, the larvae gathered at the bottom of the watch
glass.
Stage III: The final narcotizing solution contained ben-
zocaine (ethyl-4-aminobenzoate) and procaine hydrochlo-
ride (Table 1). The MgCl, solution was gradually re-
placed with this mixture, which was added to a full watch
glass to minimize turbulence. The veligers were left in it
for approximately 10 min until the cilia stopped beating.
Benzocaine is a widely used narcotic for fish (e.g.,
McERLEAN & KENNEDY, 1968), but if applied without
Stages I and II caused retraction.
At any stage in the procedure until the cessation of
Page 230 ihe Veliger, VicleZomNoms
— 0 "6 ooo" y gv oof 20
r i Sn! p 3
t
5
Explanation of Figures 1 and 2
Figure 1. Frontal SEM view of a 4-wk-old veliger with the velar Figure 2. TEM view of the velar food groove with pre-oral cilia
lobes in the extended position. The opening of the mantle cavity above and post-oral cilia below. A mass of mucous cells lies
can be seen dorsally between the two lobes. Below the velum is internal to the groove. Scale bar = 2 wm.
the foot and part of the operculum. Scale bar = 50 um.
P. Stirling et al., 1984 Page 231
Table 1
Composition of solutions.
Calcium-free seawater MgCl, Final narcotizing solution
(g/L distilled water) (g/L distilled water) (g/5 mL ethanol) Fixative
NaCl 33.5 MgCl,-6H,O 75
MegCl,-6H,O 123)
Na,SO, 39)
KCl 0.66
NaHCo, 0.4
ciliary beating, the narcotization can be reversed by re-
placing the fluid surrounding the larvae with seawater.
Fixation: A few drops of fixative (see Table 1) were added.
The fixative reacted with the final narcotizing solution, so
most of the fluid in the watch glass was removed rapidly
and fresh fixative added. This procedure was repeated
twice.
After fixation, veligers were rinsed several times in 0.1
M cacodylate buffer and postfixed in 1% OsO, in 0.1 M
cacodylate buffer. The larvae were then ready for dehy-
dration and preparation for SEM by critical point drying.
For TEM and LM, veligers were embedded in resin.
Thick sections (for LM) were cut with glass knives. We
did not use decalcification techniques such as those de-
scribed by BONAR & HADFIELD (1974), but cut thin sec-
tions (for TEM) using a diamond knife.
Results: Thirty to fifty percent of specimens were fixed
successfully with the velum completely extended. The re-
mainder had partly extended velar lobes, and very few
were completely closed. The method was more successful
with newly hatched veligers than with those 4-5 weeks
old and about to metamorphose. Figure 1 shows a 4-wk-
old veliger with the velar lobes fully extended. Figure 2
shows a TEM section of one of the velar lobes.
DISCUSSION
Although the early work of CARTER (1926) identified nic-
otine as a useful narcotic for the velar cilia of veliger
larvae, MACKIE et al. (1976) found magnesium chloride
more effective as a general narcotic for veligers of Man-
gelia. Our observations showed that MgCl, did narcotize
the veligers of Amphibola, but under this narcosis they
were still capable of retracting into the shell upon addition
of fixative. The procedure described here prevented this
reaction.
Although SEM has been a useful tool in describing the
shells of larval gastropods (e.g., ROBERTSON, 1972;
THIRIOT-QUIEVREUX & SCHELTEMA, 1982), and has been
used to examine bivalve larvae (e.g., LUTZ et al., 1982),
we have been able to find only one previous use of SEM
showing veligers with expanded velar lobes (CHIA & Koss,
1978). Even in this case, the velum was not completely
Benzocaine 0.1
Procaine 0.002
Add to this 45 mL
50% seawater
2.5% glutaraldehyde
in 0.1 M cacodylate
buffer at pH 7.6
(Should be made up
(Must be made up imme- fresh each day.)
diately before use.)
expanded into the swimming position. We have not yet
been able to test the technique described here on other
veligers, but if our three-stage approach can be applied to
a wide range of gastropod larvae, it should allow wider
use of electron microscopy to describe both their external
surface and their internal structure.
ACKNOWLEDGMENTS
We are grateful to Gerald Stokes for help with critical
point drying and SEM. One of us (C.L.) was supported
by a Leverhulme Fellowship and a William Evans Vis-
iting Fellowship while at the University of Otago; P.S.
and C.L. wish to thank Professor D. D. McGregor and
Professor J. B. Jillett for the facilities provided.
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PILKINGTON, M. C. & J. B. PILKINGTON. 1982. The plank-
Page 232 The Veliger, Vol. 26, No. 3
tonic veliger of Amphibola crenata (Gmelin). J. Moll. Stud. THIRIOT-QUIEVREUX, C. & R. S. SCHELTEMA. 1982. Plank-
48:24-29. tonic larvae of New Zealand gastropods. V. Bittvum alter-
ROBERTSON, R. 1972. Scanning electron microscopy of plank- natum, Triphora nigrocincta, Cerithiopsis emersoni, Lunatia
tonic larval marine gastropod shells. Veliger 14:293-297. heros and Crepidula plana. Malacologia 23:37-46.
The Veliger 26(3):233-239 (January 3, 1984)
THE VELIGER
© CMS, Inc., 1984
New Species of Northeast Pacific Archaeogastropods
JAMES H. McLEAN
Los Angeles County Museum of Natural History, 900 Exposition Boulevard,
Los Angeles, California 90007
Abstract. Eight new archaeogastropods from the northeastern Pacific are described: Anatoma bax-
teri, Puncturella rothi, Margarites hickmanae, Calliostoma titanium, C. bernardi, Lirularia discors,
Halistylus genecoam, and Homalopoma draperi.
THE NEW SPECIES described here are to be included in a
report on the rhipidoglossate archaeogastropods of the
northeastern Pacific from Alaska to Baja California
(McLean, in preparation). Generic and subgeneric allo-
cations are discussed in that work, which also includes
new subfamilial classifications.
Abbreviations for the museum collections mentioned in
the text are: AHF, Allan Hancock Foundation (collection
at LACM); CAS, California Academy of Sciences, San
Francisco; LACM, Los Angeles County Museum of Nat-
ural History; NMC, National Museum of Canada, Ot-
tawa; USNM, National Museum of Natural History,
Washington.
Family SCISSURELLIDAE
Anatoma Woodward, 1859
Anatoma baxteri McLean, spec. nov.
(Figure 1)
“Scissurella (Anatoma) lamellata (A. Adams, 1862), Mc-
LEAN, 1967:406. Not Anatomus lamellatus A. Adams,
1862.
Description: Shell small for genus, low-spired, fragile,
translucent grayish white. Protoconch diameter 0.2 mm;
teleoconch whorls 2%; first teleoconch whorl smooth,
rounded; suture deeply impressed in first quarter whorl;
fine axial ribs appear in second quarter, selenizone ap-
pearing in fourth quarter of first whorl. Selenizone at
periphery, slit open '/, of circumference, bordered by sharp
raised edges. Axial sculpture of sharp, thin ridges, curved
protractively near suture on upper half of whorl, retrac-
tively curved across base. Spiral sculpture of fine striae
throughout, much weaker than axial ribs and not crossing
them. Peritreme complete at all growth stages; umbilicus
partially obscured by reflection of inner lip. Suture laid
below lower bordering ridge of selenizone, forming deep
channel of same width as selenizone; suture descending
slightly on last quarter of final whorl, increasing width of
subsutural channel to twice that of selenizone.
Dimensions: Height 1.8 mm, diameter 2.3 mm (holo-
type).
Type material: 30 specimens from the type locality (many
in poor condition), dredged by Rae Baxter and James H.
McLean, 2 August 1973. Holotype LACM 1991, 25
paratypes LACM 1992, 2 paratypes CAS 033360, 2
paratypes USNM 784743.
Type locality: 9 m off N side Hesketh Island, Kachemak
Bay, Kenai Peninsula, Cook Inlet, Alaska (59°30.5'N;
IS MES TO VAY).
Referred material: 5 lots in the LACM collection, from
the type locality east to Torch Bay, Glacier Bay National
Monument, Alaska, in depths of 10-45 m on gravel and
mud bottoms. Specimens from Torch Bay were collected
by Tom Suchanek.
Comparisons: I previously (MCLEAN, 1967) identified
this species as Scissurella (Anatoma) lamellata (A. Adams,
1862), which occurs at 50-700 m in central Japan (KURO-
DA et al., 1971; other references in MCLEAN, 1967). This
species differs from the latter in its smaller size (maximum
diameter of 2.3 mm rather than 3.5 mm), and lenticular
rather than high-turbinate profile. It is the only eastern
Pacific species of Anatoma having the axial sculpture much
stronger than the spiral sculpture.
Remarks: I follow POWELL (1979) in regarding the dif-
ferences between Scissurella Orbigny, 1824, and Anatoma
at the generic rather than subgeneric level.
Named after Rae Baxter, Alaska Department of Fish
and Game, Bethel, Alaska, who has collected this species
from many localities in Alaska.
Page 234
Figure 1
Anatoma baxteri McLean, spec. nov. Three views of holotype;
height 1.8 mm.
Family FISSsURELLIDAE
Puncturella Lowe, 1827
Puncturella rothi McLean, spec. nov.
(Figure 2)
Description: Shell of moderate size for genus, relatively
thin; basal outline elongate oval, narrower anteriorly; sides
distinctly compressed, nearly parallel. Anterior slope
slightly convex, posterior slope slightly concave, lateral
slopes nearly straight. Apex approximately central, erod-
ed to blunt, posteriorly directed spur. Foramen long and
narrow, constricted in middle, anterior portion narrowed
and tapering. Radial sculpture of approximately 30 strong
primary ribs originating near apex, secondary ribs emerg-
ing when shell is half-grown; secondary ribs not quite
attaining same size as primary ribs, but filling interspaces;
ribs finely and sharply beaded corresponding to growth
increments. Exterior pattern of radial sculpture visible in
shell interior; muscle scar not apparent; margin finely
crenulated by primary ribs. Septum broadly arched, slant-
ed forward, anteriormost extension of septum continuous
with wedge-shaped callus that borders foramen, termi-
nating 3 mm from anterior margin; base of septum with
weak lateral extensions or props.
Dimensions: Length 15.0 mm, width 10.5 mm, height 8.0
mm (holotype).
Type material: 4 specimens (1 with remains of mantle
tissue, indicating that it was live-collected) from the type
locality, collected by the R/V “N. B. Scofield,” station
B.8, 6 October 1950. Holotype CAS 033361, paratype
CAS 033362, paratype LACM 1993, paratype USNM
784744.
The Veliger, Vol. 26, No. 3
Type locality: 521-283 m (285-155 fm), Delgada Can-
yon, off Buck Creek (approximately 40°05'N; 124°08’W),
Humboldt County, California.
Comparisons: Puncturella rothi differs from P. galeata
(Gould, 1846) in its smaller size, more parallel sides,
stronger development of beaded sculpture, larger septum,
larger foramen, and absence of sharp ridges that form
props to the septum.
Remarks: Puncturella rothi is known only from the type
lot. It has the general appearance of Cranopsis decorata
(Cowan & McLean, 1968), but does not have the anterior
seam in the shell nor the split mantle roof that distin-
guishes Cranopsis A. Adams, 1860. All specimens have
the apical area eroded. This species occurs at depths great-
er than those of other eastern Pacific species of Punctu-
rella; it lives at depths characteristic for Cranopsis decorata.
Named after Dr. Barry Roth of the California Acade-
my of Sciences, San Francisco.
Family TROCHIDAE
Margarites Gray, 1847
Margarites hickmanae McLean, spec. nov.
(Figures 3, 9)
“Margarites beringensis E. A. Smith,” DALL, 1925:19, pl.
36, figs. 4, 6. Not Valvatella beringensis E. A. Smith,
1889.
Description: Shell moderately large for genus, cream-col-
ored under thin, pale brown, shiny periostracum. Proto-
conch smooth, tip pointed, protoconch diameter 0.35 mm;
teleoconch whorls 5; early suture slightly impressed, be-
coming deeper on later whorls; suture gradually descend-
ing on final whorl. Last whorl broadly inflated; aperture
markedly oblique, umbilicus narrow. Peritreme nearly
complete; inner lip thick, parietal lip reflected, almost
blocking umbilicus. Spiral sculpture of fine, microscopic
incised lines, about 24 on penultimate whorl, 18 on body
whorl; axial sculpture of fine growth lines. Interior iri-
descent, chiefly lavender. Lateral teeth of radula 7 pairs,
overhanging tips long and tapered, tips rounded, both edges
finely denticulate.
Dimensions: Height 10.1 mm, diameter 12.2 mm (holo-
type).
Type material: 14 specimens (all but one specimen live-
collected and dried with opercula in place) from the type
locality, dredged by the U.S. Fisheries Commission R/V
“Albatross,” station 4779, 5 June 1906. Holotype, USNM
111048, 9 paratypes USNM 205827, 2 paratypes LACM
1994, 2 paratypes CAS 033363.
Type locality: 99 m (54 fm) on sand and shell bottom,
Petrel Bank (near Semisopochnoi Island, Rat Islands,
Aleutian Islands), Bering Sea, Alaska (52°11'N;
179°57'W).
J. H. McLean, 1984
Page 235
Explanation of Figures 2 to 8
Figure 2. Puncturella rothi McLean, spec. nov. Three views of
holotype; length 15.0 mm.
Figure 3. Margarites hickmanae McLean, spec. nov. Two views
of holotype; height 10.1 mm.
Figure 4. Calliostoma titanium McLean, spec. nov. Holotype;
height 32.2 mm.
Figure 5. Calliostoma bernardi McLean, spec. nov. Holotype;
height 25.7 mm.
Referred material: Known only from the type lot.
Comparisons: This is the only member of Margarites, s.s.,
in which there are 7 pairs of lateral teeth in the radula
(Figure 9). Such similarly proportioned, shallower occur-
ring species as M. helicinus (Phipps, 1774), M. beringensis
Figure 6. Calliostoma bernardi McLean, spec. nov. Paratype;
height 26.5 mm.
Figure 7. Lirularia discors McLean, spec. nov. Two views of
holotype; height 4.3 mm.
Figure 8. Homalopoma drapert McLean, spec. nov. Three views
of holotype; height 4.0 mm.
(E. A. Smith, 1899), and M. albolineatus (E. A. Smith,
1899) lack spiral sculpture and have 6 pairs of lateral
teeth in which the tips of the outer laterals are broader
than those of M. hickmanae. In size the new species most
resembles the offshore M. gigantea (Leche, 1878), but that
species has 4 pairs of lateral teeth, a less inflated final
Page 236
Figure 9
Margarites hickmanae McLean, spec. nov. Half row of radula
of holotype, showing rachidian at left, 7 marginal teeth, latero-
marginal plate, and first 2 marginal teeth.
whorl, and a darker, dull-surfaced periostracum. Marga-
rites hickmaneae is larger than M. argentata (Gould, 1841),
which has 5 pairs of lateral teeth. (M. pribiloffensis Dall,
1919, is here regarded as a synonym of M. argentata, the
holotype having 5 pairs of laterals.)
Remarks: The holotype of M. hickmanae was figured by
DALL (1925) under the name M. beringensis (E. A. Smith,
1899), a species described from the Commander Islands
(west of the westernmost of the Aleutian Islands). Mar-
garites beringensis differs in having a glossy brown surface
and gray early whorls; it is common at low tide in Alaska
and British Columbia.
The name honors Dr. Carole S$. Hickman of the De-
partment of Paleontology, University of California,
Berkeley.
Calliostoma Swainson, 1840
Calliostoma titanium McLean, spec. nov.
(Figure 4)
Description: Shell large for genus, sturdy, white, proto-
conch diameter (of smallest specimen) 0.4 mm, teleoconch
whorls 7. Whorls only slightly rounded, shoulder slightly
tabulate; base defined by moderately sharp keel. First 3
teleoconch whorls with strong, unbeaded spiral cords; spi-
ral sculpture of subsequent whorls very subdued except
for subsutural cord; subsutural cord prominently beaded
on fifth whorl; fine, even spiral cords emerge on fifth whorl;
16 spiral cords on penultimate whorl; all cords micro-
scopically beaded on final whorl. Suture laid upon basal
angulation; base imperforate, smooth, with fine spiral
striae, more strongly developed near columella. Aperture
quadrate, outer lip thin, columella thick, slightly reflected.
Interior iridescent pink and green.
Dimensions: Height 32.2 mm, diameter 30.0 mm (holo-
type); height 27.4 mm, diameter 25.3 mm (paratype).
The Veliger, Vol. 26, No. 3
Type material: 2 specimens from the type locality dredged
by the R/V “Velero,” station 1027-39, 10 December 1939.
Holotype LACM 1995, paratype USNM 784745.
Type locality: 256-274 m (140-150 fm) on green mud,
8.3 km (5 miles) SE of Santa Catalina Island, California
(33°15'N; 118°14'W).
Referred material: Two additional specimens: one
(LACM-AHF 1151-40), 214-234 m (117-128 fm) near
type locality (33°16'N; 118°16’W), collected 5 July 1940,
height 29.5 mm, diameter 28.4 mm; and one (LACM
92119), from 300 m, “Cortes Bank,” California, collected
August, 1968, by Shane Anderson, height 18.8 mm, di-
ameter 17.7 mm.
Comparisons: Although Calliostoma titanium has its third
and fourth whorls without spiral sculpture, as in C. plat-
inum Dall, 1890, it differs from the latter in having a
sturdier shell, a subsutural tabulation, and numerous fine
cords on the final whorl. It is larger than C. bernard
McLean, spec. nov., from which it also differs in having
the third and fourth whorls smooth rather than having
strong spiral cords on all whorls; the cords on the body
whorl are more numerous and finer than those of C. ber-
nardi.
Remarks: This and the following new species have been
known to me for many years, not having been described
until now in the futile hope of obtaining more material.
The name is that of a metallic element, emphasizing
lack of shell color, and contrasting with C. platinum.
Calliostoma bernardi McLean, spec. nov.
(Figures 5, 6)
Description: Shell medium-sized for genus, sturdy, white;
protoconch diameter 0.4 mm, teleoconch whorls 7/2. Early
whorls flat-sided except for strongly projecting subsutural
cord; final whorl rounded, losing sharp basal angularity
of previous whorl. First 3 teleoconch whorls with 3 strong,
unbeaded spiral cords, intercalary cords of lesser strength
appearing on fourth whorl; original cords becoming bead-
ed on fourth whorl; penultimate whorl with 9 somewhat
irregular cords, uppermost of these beaded; body whorl
with about 13 cords above ill-defined periphery, upper-
most of these finely beaded. Base imperforate, mostly
smooth but for fine spiral striae, basal cords more strongly
developed toward columella. Aperture rounded, outer lip
thin, columella thick. Interior iridescent pink and green.
Dimensions: Height 25.7 mm, diameter 22.8 mm (holo-
type); height 26.5 mm, diameter 22.8 mm (paratype).
Type material: Holotype LACM 1996; single specimen
only from type locality, collected by the R/V “Velero,”
AHF station 1152-40, 5 July 1940. One paratype, NMC
86653, 128 m (70 fm), Halibut Bank, Georgia Strait,
British Columbia (49°18'42”N; 123°41'06”W), collected
by Frank R. Bernard, ‘11 October 1968.
J. H. McLean, 1984
Type locality: 241-271 m (132-148 fm), off SE end
of Santa Catalina Island, California (33°15'40’N,
118°13’25”"W).
Comparisons: Calliostoma bernardi is closest to C. tita-
nium McLean, spec. nov., but is smaller and has pro-
nounced spiral sculpture at all growth stages, rather than
having the nearly smooth third and fourth whorls of both
C. titanium and C. platinum Dall, 1890.
Remarks: Although only two specimens from well sepa-
rated localities are known, the fact that they are conspe-
cific argues against the possibility that this is a variant of
C. titanium, which would be a major concern if only the
southern specimen were known. I prefer not to designate
paratypes from other than the type locality, but make an
exception in this case.
Named after Dr. Frank R. Bernard, of the Fisheries
Research Board of Canada, Nanaimo, British Columbia,
who submitted the paratype specimen.
Lirularia Dall, 1909
Lirularia discors McLean, spec. nov.
(Figure 7)
“Lirularia succincta (Carpenter),’ MCLEAN, 1969:21, fig.
8-3. Not Gibbula succincta Carpenter, 1864.
Description: Shell medium-sized for genus; color varie-
gated dark brown and cream, cord interspaces with yel-
lowish green metallic luster, particularly on base. Peri-
ostracum extremely thin, barely detectable. Protoconch
dark brown, diameter 0.2 mm; teleoconch whorls 4%, su-
ture distinct but not deeply impressed; aperture oblique,
umbilicus deep, narrow; peritreme interrupted in parietal
area, inner lip moderately thick, not reflected over um-
bilicus. Spiral sculpture of strong cords: rounded mid-
whorl carination on first teleoconch whorl, two cords of
lesser prominence added on second whorl; penultimate
whorl with three major cords and start of lesser, interca-
lary cords; cords on body whorl! alternating in strength.
Suture descending on final whorl to expose fourth major
cord defining base. Axial sculpture lacking except for fine
growth lines. Basal cords usually 7: two outermost cords
strong, two middle cords narrower, and three near um-
bilicus strong and broad; this produces a shallow channel
midway between basal angularity and umbilicus, produc-
ing also a slight indentation in basal lip. Umbilical wall
smooth. Interior iridescent pink and green.
Dimensions: Height 4.3 mm, diameter 4.3 mm (holo-
type).
Type material: 60 specimens from the type locality, col-
lected by James H. McLean, 12 August 1963. Holotype
LACM 1997, 49 paratypes LACM 1998, 5 paratypes
CAS 033364, 5 paratypes USNM 784746.
Type locality: 4-7 m on rocky bottom, south side of Pun-
Page 237
ta Banda (near the blowhole), Baja California Norte,
Mexico (31°43.6'N; 116°43.0’W).
Referred material: 62 additional lots are in the LACM
collection, from numerous localities between Pacific Grove,
California, and Isla Cedros, Baja California. The species
is common in rocky intertidal and sublittoral zones to 20
m, particularly in areas with cool upwelling.
Comparisons: This differs from L. succincta (Carpenter,
1864) in having stronger spiral cords, a more angulate
base, and a color pattern of variegated brown and white,
rather than uniform gray. Both species have the same kind
of broad channel on the base, a feature shared by no other
member of the genus. Lirularia optabilis (Carpenter, 1864)
is a much larger species restricted to and common in the
Pleistocene of southern California. Lirularia acuticostata
(Carpenter, 1864) differs in having regular, sharp axial
lamellae.
Remarks: Lirularia succincta, the species most closely re-
lated to L. discors, occurs from Cook Inlet, Alaska, to
Piedras Blancas Point, San Luis Obispo County, Califor-
nia. Both species are sympatric in central California be-
tween the Farallon Islands and San Luis Obispo County.
Here the habitat is partitioned: L. succincta is abundant
in the intertidal zone and L. discors occurs in the shallow
sublittoral zone, as shallow as 2 m. South of the range of
L. succincta, L. discors is sublittoral, and, in areas of cool
upwelling (as at the type locality), it is also intertidal.
The name is a Latin adjective, meaning “different.”
Halistylus Dall, 1890
Halistylus genecoant McLean, spec. nov.
(Figure 10)
Description: Shell small (normal for genus), sturdy, high-
spired; nacreous interior lacking. Protoconch diameter 0.2
mm; teleoconch whorls 7, first 3 whorls low spired, dome-
shaped in profile; 4 final whorls turritelliform, evenly ex-
panding, the periphery either bulging or somewhat an-
gulate at lower % of whorl, profile nearly straight on
upper *% of whorl. First teleoconch whorl smooth, round-
ed, suture not deeply impressed. Second whorl with 5
strong, broad, low, spiral cords; first, third, and fifth cords
more prominent, interspaces deeply channeled; third and
succeeding whorls with addition of narrow cords in inter-
spaces between major cords. Mature sculpture of 4 broad,
rounded cords spaced across lower % of whorl, interspaces
about twice breadth of major cords and filled by about 3
fine cords between each large cord; upper third of whorl
with about 4-6 fine cords of varying strength. Subsutural
cord strong, sharply defining the incised suture. Base with
about 7 strong, flat-topped cords; interspaces of equal
width, having 1-3 narrow, sharp cords, separated by deep
incisions. Aperture circular, peritreme of juvenile shell
incomplete, lip of young shells sharp, crenulated by spiral
Page 238
Explanation of Figures 10 and 11
Figure 10. Halistylus genecoani McLean, spec. nov. Holotype;
height 5.6 mm.
Figure 11. Halistylus pupoideus (Carpenter). LACM 75-96, 18
m off Torrance Beach, Los Angeles County, California; height
4.7 mm.
cords; columellar lip raised over an umbilical chink. Ma-
ture lip beveled, thickened within; aperture slightly
oblique, peritreme complete; parietal and columellar lip
sharp and slightly raised; suture descending at final stage,
outer lip greatly thickened below suture. Color white, yel-
low or tan, with irregular dark flammules. Operculum
typical for genus: circular, multispiral, early volutions in-
distinct; 5 volutions showing on outer *% of radius, each
volution with projecting edge.
Dimensions: Height 5.6 mm, diameter at aperture 4.4
mm (holotype).
Type material: 37 specimens (2 with opercula) collected
by diving at type locality by Camm Swift and Richard W.
Huddleston, R/V “Searcher” station 281, 24 October
1971. Holotype LACM 1999, 30 paratypes LACM 2000,
3 paratypes CAS 033365, 3 paratypes USNM 784747.
Type locality: 20-24 m, sandy bottom outside of kelp
beds, cove at S side of Punta San Pablo, outer coast of
Baja California Sur, Mexico (27°12'55”N; 114°27'30”W).
Referred material: 6 additional lots in the LACM col-
lection, from depths of 13-55 m; 4 lots from the vicinity
of the type locality in central Baja California (near Bahia
San Cristobal, Isla Natividad, Bahia Tortuga, and Thur-
loe Head), and 2 lots from southern Baja California (Ba-
hia Santa Maria and Arroyo Conejo).
Comparisons: Halistylus genecoani differs from H. pu-
poideus (Carpenter, 1864) (Figure 11) in having a cari-
nate rather than rounded profile, spiral cords of different
strength and spacing, and a less deeply impressed suture
he Veliger, VolyZomNows
in the first two whorls. The two species have both broad
and narrow spiral cords, but the broad cords of H. gene-
coani are fewer and broader than those of H. pupoideus.
The depth of the suture in the early whorls provides the
best distinguishing character, that of H. pupoideus being
more deeply impressed than that of H. genecoant.
Remarks: Both Halistylus pupoideus and H. genecoan
exhibit considerable variation in strength and spacing of
the spiral cords, both species having extreme forms that
approach the sculpture of the other. Some specimens of
H. pupoideus have major cords more prominent than nor-
mal, and some of the paratypes of H. genecoami have
more rounded whorls than those of the holotype. In both
species the infraspecific range of variation is greater than
the interspecific difference separating extreme forms of the
two species. Distributions of the two species are sympatric
at 27°N latitude; however, there are too few records from
the region of overlap to establish whether there are habitat
differences between the two species.
The species is named after Dr. Eugene Coan, Research
Associate of the Los Angeles County Museum of Natural
History.
Family TURBINIDAE
Homalopoma Carpenter, 1864
Homalopoma draperit McLean, spec. nov.
(Figure 8)
Description: Shell medium-sized for genus, relatively low-
spired; whorls 3, rounded; periphery rounded, suture
deeply impressed, descending on final half whorl. Color
pink, usually white in area of umbilical chink; some spec-
imens with white flecks on spiral cords and predominantly
white base. Protoconch diameter 0.2 mm; early whorls
rounded, suture deeply impressed; early cords about 8-9,
broad, even, low, with narrow interspaces; interspaces of
later whorls broader than cords and with 2-3 fine cords
or striae. Mature cords of irregular strength and spacing;
cords on shoulder often slightly undulating. Periphery
rounded, basal sculpture variable; basal cords up to 10,
weaker than cords of upper part of whorl; some specimens
with 2-3 broadly spaced stronger cords on base, others
with more regular basal cording. Half-grown specimens
narrowly umbilicate; umbilicus nearly blocked by parietal
callus. Aperture of mature specimens markedly oblique;
parietal callus broad, covering umbilical chink and form-
ing projecting inner lip; callus extending in advance of
aperture on base, forming distinct glazed area. Columella
with one prominent tubercle. Operculum typical for ge-
nus, opaque white, externally showing 2-3 volutions,
thickened on side toward columella.
Dimensions: Height 4.0 mm, diameter 4.8 mm (holo-
type); height 5.3 mm, diameter 5.8 mm (largest paratype).
Type material: 175 specimens (5 live-collected), collected
J. H. McLean, 1984
by diving at the type locality by James H. McLean, June
and July 1971. Holotype LACM 2001, 164 paratypes (2
live-collected) LACM 2002, 5 paratypes (1 live-collected)
CAS 033366, 5 paratypes (1 live-collected) USNM
784748.
Type locality: 20-30 m on gravel bottom below the boul-
der and kelp zone, Isthmus Cove, Santa Catalina Island,
California (33°26.5'N; 118°29’W).
Referred material: 42 additional lots are in the LACM
collection, mostly from depths of 20-100 m (some dead
specimens from greater depths) in the vicinity of all the
southern California Channel Islands (except San Miguel
and Santa Barbara Islands). It replaces Homalopoma lun-
dum (Dall, 1885) on gravel bottoms deeper than the un-
der-kelp habitat favored by the latter at the Channel Is-
lands. The southern record is Cortes Bank, California, 68
m (LACM-AHF 1335-41). North of the Channel Is-
lands, H. draperi is known from a single station, 35 m
off Pacific Grove, Monterey Bay (LACM 66-56). It is
well represented in lower Pleistocene faunules from many
offshore facies in southern California, including the Bath-
House Cliff locality of the Santa Barbara Formation.
Comparisons: Homalopoma draperi is characterized by
its low spire, numerous subdued early cords, mature
sculpture that includes some cords more prominent than
others on the body whorl and base, and the callus depos-
ited on the base in advance of the aperture. Homalopoma
grippi (Dall, 1911) is higher-spired; the latter species also
has subdued basal cords, but differs in having fewer, more
projecting cords on the early whorls. Homalopoma luridum
differs in always having prominent cords of the same
strength on the spire whorls and base. There is also some
resemblance to H. paucicostatum (Dall, 1871) in the rel-
atively few major cords on mature whorls, but that species
has fewer early cords.
Page 239
Remarks: This species is by far the most variable eastern
Pacific Homalopoma. Although none has been illustrated
previously, it has long been a source of confusion in col-
lections. Some specimens are nearly devoid of sculpture,
and some have rather uniform cords. These variants may
be recognized as H. draperi in having cords on the base
finer than those of the upper part of the whorl and in
having a glazed basal callus.
Named after Bertram C. Draper of Los Angeles, whose
photographs have illustrated many papers on eastern Pa-
cific mollusks.
ACKNOWLEDGMENTS
I am grateful to the following collectors for the donation
of type or referred material of the new species: Shane
Anderson, Rae Baxter, Frank R. Bernard, Richard W.
Huddleston, Tom Suchanek, and Camm Swift. Loans of
type material were arranged by Barry Roth (CAS) and
Joseph Rosewater (USNM). The photographs for the new
species of Anatoma were taken by Bertram C. Draper of
Los Angeles. Assistance in the preparation of other figures
was provided by the LACM photography lab. I thank
Eugene Coan, Myra Keen, and Patrick I. LaFollette for
reading the manuscript and offering helpful suggestions.
LITERATURE CITED
Dat, W. H. 1925. Illustrations of unfigured types of shells
in the collection of the United States National Museum.
Proc. U.S. Nat. Mus. 66(2554):1-41.
Kuropa, T., T. HABE & K. OyAMA. 1971. The sea shells of
Sagami Bay. Maruzen, Tokyo. xvi + 741 + 487 + 51 pp.
McLean, J. H. 1967. West American Scissurellidae. Veliger
9:404-406.
McLean, J. H. 1969. Marine shells of southern California.
Los Angeles County Museum of Natural History, Science
Series, no. 11, 104 pp.
PowELL, A. W. B. 1979. New Zealand Mollusca. Collins,
Auckland. xiv + 500 pp.
The Veliger 26(3):240 (January 3, 1984)
THE VELIGER
© CMS, Inc., 1984
NOTES, INFORMATION & NEWS
In Memory of S. Ralph Hall
The members of the Long Beach Shell Club have made
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this donation with gratitude, and extends its sympathy to
Mrs. Hall.
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CONTENTS — Continued
The opisthobranch mollusks of Humboldt County, California.
WiaLLIAM Bo JAR CK ws (A0 ae ctue eh aloes oe 4 Merten te ict iar ee 207
Doridacean nudibranchs from Sri Lanka, with descriptions of four new species.
INATHABIE: YONOW joi)uti i a Mik Waleed rea sa ea! Sau eu ey sisi Gna an ae 214
Technique for narcotizing and fixing veliger larvae of Amphibola crenata.
PENNY STIRLING, COLIN LITTLE, MARGARET C. PILKINGTON, AND JOHN B.
PILKINGTON 5.0550 onc 3 Suc ee re 2s Contre a Arg aoe ea eS AS a ee 229
New species of northeast Pacific archaeogastropods.
JAMES Hi) MIGIEBAIN® ota) 020 LM aOR ah ach Caer Ne Ciena Uc Helen er ieee Z2)2)
Notes, Information & News.
Bite C2 5O
VES ISSN 0042-3211
L101. os PAM H. AIT.
THE DIVision ae LIBRARY
| F MOLLUSKS
A Quarterly published by
CALIFORNIA MALACOZOOLOGICAL SOCIETY, INC.
Berkeley, California
R. Stohler, Founding Editor
Volume 26 April 2, 1984 Number 4
CONTENTS
Supplementary information on the morphology of Phestilla melanobranchia Bergh,
1874, from Seto, Kii, Middle Japan (Nudibranchia: Aeolidacea: Tergi-
pedidae).
I TURUUITBATRG): BYTES 3 ch coe alten alee ray Ae UO PP gh a 241
Distributional records for terrestrial and freshwater Mollusca of the Cascade
and Coast ranges, Oregon.
BRANLEY ALLAN BRANSON AND ROGERS MACGOWAN BRANSON ......... 248
The biology of the northeastern Pacific Turridae. IV. Shell morphology and
sexual dimorphism in Aforia circinata (Dall, 1873).
JRGINZAILID) Lye (SUBMENU SIG 2a ik eum Sane eae uate Mia A TIA este ay UE eaci rss) pr par 258
Distribution and radular morphology of various nudibranchs (Gastropoda: Opis-
thobranchia) from the Gulf of California, Mexico.
TANS DS ERSISCHPANIDEAILE: ISPRSIRIMCH 00) 20 hes Se es 264
The diets of Alaskan Neptunea.
CONT ANIBID BE aS ETTIN AE Keser ah Ste ee ts Seung eS) URS Ak Bee ecg Ne ee Np ll 274
Spatial distribution of three species of bivalves on an intertidal flat: the inter-
action of life-history strategy with predation and disturbance.
IAL AN” Lig TBKOSICAN CIN Aaa aM ee age ie OD Sind ate See Ala 282
Orientational and anatomical trends related to detorsion among prosobranch
gastropods.
WOWISHEe GAINEYAi) Re ANDY GEARILES R= SITASEK ) 26 aia ceca ia sees aie: 288
CONTENTS — Continued
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The Veliger 26(4):241-247 (April 2, 1984)
THE VELIGER
© CMS, Inc., 1984
Supplementary Information on the Morphology of
Phestilla melanobranchia Bergh, 1874, from Seto, Kil,
Middle Japan (Nudibranchia: Aeolidacea: Tergipedidae)
by
KIKUTARO BABA
Shigigaoka 35, Minami-11-jyo, Sango-cho, Ikoma-gun, Nara-ken, Japan
Abstract.
Four orange specimens of Phestilla melanobranchia Bergh, 1874, collected from the sea of
Seto, Kii, Middle Japan, were kept alive in the laboratory, and the consistency of their orange pig-
mentation was observed. The external body form with simple branchial rows on the back margins was
determined from fresh material. A histological examination of the branchial papillae was also made.
In the main features of the jaws and radular teeth, the Japanese orange-colored specimens agreed well
with the black-colored type-specimens of Phestilla melanobranchia from the Philippines to which the
former was referred. Comprehensive anatomical information on the copulatory part of the genitalia is
given for Phestilla melanobranchia for the first time.
INTRODUCTION
RECENTLY THERE appeared three successive papers by
RUDMAN (1981, 1982a, b) concerning the genus Phestilla
from Tanzania, Queensland (Australia), and the Bay of
Panama (Mexico). Previous to him, the highly modified
life of Phestilla in association with prey corals had been
the subject of studies by KAWAGUTI (1943) and HARRIS
(1968) on the basis of specimens obtained by them from
several stations in the central Pacific and southwest Pa-
cific, including Japan. Fortunately I was able to contact
each of them in order to identify the specimens of Phestilla
they studied.
Phestilla sibogae Bergh, 1905, which appeared in Ka-
WAGUTI (1943), was based on a specimen (25 mm long
when alive, and 10 mm long when preserved) collected on
Porites from Palau, 29 March 1940 (Figure 1). According
to RUDMAN (1981) this name was preoccupied by C7a-
tena? lugubris Bergh, 1870, which also had priority over
Aeolidia edmondsoni Ostergaard, 1955. The species Phes-
tilla lugubris (Bergh, 1870) was thus revealed to be dis-
tributed over a wide range between the Indian Ocean,
southwest Pacific, and central Pacific. Up to now this
species has appeared to be well studied anatomically and
ecologically by different authors.
Phestilla melanobranchia, which formed the subject of
work by HarRIs (1968), was established by BERGH (1874)
on the basis of preserved specimens from the Philippines.
Apparently the species was so named because of the pos-
session of black (schwarzgrau oder schwarz) papillae on
the back margins. However, HARRIS (1968) noted that the
papillae of Phestilla melanobranchia in his collection varied
between orange and black depending on the specimen.
The purpose of this paper is to describe live specimens
of orange-colored Phestilla from Japan, their identification
being assured by a series of features that were originally
known from the black type-specimens of Phestilla mela-
nobranchia. Moreover, it is hoped that this paper will offer
more extensive morphological information on this species.
TAXONOMY or MATERIALS
Phestilla melanobranchia Bergh, 1874
(orange color form)
(Japanese name: Iboyagi-mino-umiushi)
(Figures 2 to 5)
Main synonymy:
Phestilla melanobranchia. HARRIS, 1968:193-198, figs. 1-2;
Hawaii; Seto, Kii; Okinawa; Zamboanga (Philippines);
Singapore; on 7ubastraea.
Refer also to: EDMONDSON (1946), Kay (1979),
GOSLINER (1980), BERTSCH & JOHNSON (1981),
and RUDMAN (1981).
Main material examined: Four specimens collected from
Seto, Kii, Middle Japan, 1-4 m deep, L. Harris collector,
19 September 1967. These were found on orange colonies
of Tubastraea aurea (see HARRIS, 1968:196).
Specimen No. 1. Bright orange individual; length 20 mm.
Kept alive for about 50 days; at first fed with Tubastraea
Page 242
Figure 1
Phestilla lugubris (Palau, 29 Mar. 1940, Kawaguti coll.). A. pre-
served and contracted animal from dorsal side, length 10 mm;
B. the same from ventral side; C. tooth (x 360), the radular
formula was 32 x 0.1.0, and the denticles numbered 7 to 12 on
either side, denticles on jaw edge were missing. a. genital orifices;
b. anus; c. branchial papilla tipped with a nipple.
flesh, later starved, and finally the length decreased to
10 mm.
Specimen No. 2. Orange, but slightly paler than the first;
length 15 mm. Dissected mainly for the jaws, radula,
and penis.
Specimen No. 3. Paler, only slightly tinted orange on the
The Veliger, Vol. 26, No. 4
head and the anterior half of the body; length 7 mm.
Figured for the external morphology. Fixed shortly af-
ter collecting, and prepared in serial horizontal sections.
Gonads not well differentiated.
Specimen No. 4. Juvenile, length 5 mm, a faint orange
tinge of body as in Specimen No. 3, but with the bran-
chial papillae relatively fewer in number. Fixed im-
mediately after collecting.
Additional specimen examined for comparison: One
large specimen, approximately 25 mm long when pre-
served and contracted; collected by L. Harris in Kaneohe
Bay, Oahu, Hawaii, from a Tubastraea colony, 22 June
1967 (see HARRIS, 1968:193).
DESCRIPTION
External form: The animals of Specimens No. 1 and No.
2, though relatively small in size, were mature and ca-
pable of spawning (cf. the growth and maturity in Phes-
tilla by RUDMAN, 1981:408).
The head is large and tends to form an expanded veil
(especially so after preservation). The oral tentacles are
short, the rhinophores longer, and both of these simple.
The branchial papillae, when fresh, are also simple, smooth
(not nodulose) and rounded in section. They are contrac-
tile; sometimes they can be extended considerably. Usually
they terminate each in a blunt end; at times the extreme
tip may be more-or-less instantly elevated. A group of
opaque white gland cells lies below the tip of the papillae
(see RUDMAN, 1981:402, for Phestilla lugubris). In the
present species, however, there is no marked formation of
the apical nipple of papillae known from Phestilla lugubris
(RUDMAN, 1981:375). The wall of the liver diverticulum
within the branchial papillae is minutely lobated and de-
void of zooxanthellae. A cnidosac, present in most aeolids,
is missing altogether and is replaced by a sac of clear
glandular cells (HARRIS, 1968:194; see also RUDMAN, 1981:
402, for the terminal sac of Phestilla lugubris).
In Specimen No. 3, there are 10 simple transverse rows
of papillae on back margins, of which the foremost 5 rows
are ascribed to the right liver (and the left partner) and
the rest to the left posterior liver on either side. The pa-
pillar arrangement is shown thus: 1, 3, 4, 4, 6; 4, 3, 1, 1,
1, on the right side, and 1, 3, 5, 5, 5; 4, 3, 2, 1, 1 on the
left side. The anus and nephroproct are interhepatic as
usual. The genital orifices open below the second row of
the right liver. Measurements in mm of this animal after
Risso- DOMINGUEZ (1963) were as follows: A 7; Ac 6; C
ile 183 i.S¢ lel ile JP Be I ile IR i.
The branchial papillae, deciduous and normally stand-
ing upwardly, are apt to be more crowded in the larger
specimens than in the smaller ones. When fresh they do
not appear to rest upon raised ridges or cushions (cf.
Harris, 1968:193; RUDMAN, 1981:375, for Phestilla lu-
gubris), but in Specimens No. 1 and No. 2, ridges of pa-
pillae were formed transversely by contraction of the body
after preservation. The absence of branchial ridges was
K. Baba, 1984
Page 243
Figure 2
Phestilla melanobranchia (orange form; Specimen No. 3). Living animal from dorsal (A) and ventral (B) sides. The
branchial papillae are all drawn in a horizontal plane. a. genital orifices; b. nephroproct; c. anus.
shown by RUDMAN (1981:381) in his small Phestilla minor
from Tanzania and the Great Barrier Reef, Australia.
The dorso-lateral margins are indistinct. The foot cor-
ners are rounded, the sole is expanded flat, and the tail is
short.
The animal is able to crawl in an aquarium dish, but
usually it stays on the prey corals.
Coloration: Two major colors, black and orange, were
considered by HarRRIs (1968) to be displayed by individ-
uals of Phestilla melanobranchia. These depended largely
on the dominant color pigment of the prey corals, namely
Tubastraea diaphana (green-black) and Tubastraea aurea
(orange), which passes into the branchial papillae of the
predator. Here it is suggested that the former is a black
color form (the type form), and that the latter an orange
color form, both of Phestilla melanobranchia (see HARRIS,
1968:figs. 2 and 1). But this account should be compared
Page 244
The Veliger, Vol. 26, No. 4
Figure 3
Phestilla melanobranchia (orange form). A. Specimen No. 1,
branchial papilla in extended phase, fresh; B. the same in con-
tracted phase, fresh; C. Specimen No. 3, fixed and sectioned
branchial papilla (x 84). a. isolated liver cell packed with yellow
ferment granules; b. liver diverticulum; c. group of opaque white
gland cells, fresh in A and fixed in C; d. terminal sac and an
isolated fresh glandular cell composing the sac; e. mucous cell.
with that given by RUDMAN (1981:383) on the brownish
form and the white form of Phestilla minor living on the
same Porites colony.
All the specimens I have examined belong to the orange
form mentioned above. According to my view, however,
the orange hue of these individuals seems to owe for the
most part to their natural orange pigmentation of the der-
mal epithelium. For example, Specimen No. 1 is of the
brightest orange appearance while feeding, and this color
did not noticeably diminish after it was long starved.
The general color of the body proper is orange. It be-
comes more prominently bright orange on the head and
back, and on the upper half of the oral tentacles, rhino-
phores and branchial papillae (the orange pigment gran-
ules can be seen microscopically in the epithelium of these
structures). Mostly hidden by the bright orange pigmen-
tation of the animal, clusters of opaque white dots occur
Figure 4
Phestilla melanobranchia (orange form; Specimen No. 2). A. jaw
plate (x 15); B. tooth from radular ribbon, dorsal view (x 120);
C. the same, lateral view (x 160). a. indentation; b. denticles on
jaw edge; c. median cusp.
along the length of the oral tentacles and rhinophores and
on the pericardial prominence. The liver diverticulum
within each branchial papilla is always tinted yellow ow-
ing to the yellow ferment granules which it contains. The
foot sole is always colorless.
In Specimen No. 4, which is the youngest of the four
specimens, the orange color is visible only on the head, on
the back in the anterior half, and the upper half of each
of the cephalic structures and branchial papillae. The yel-
low tint of the liver system is as in the adult specimens.
Internal anatomy: The mouth part and the pharynx are
provided each with paired oral glands and paired salivary
K. Baba, 1984
Page 245
Figure 5
Phestilla melanobranchia (orange form). A. Specimen No. 3, genital organs from dorsal side (x 100); B. Specimen
No. 2, penis and apical stylet (x 50); C. Specimen No. 1, egg mass laid on Tubastraea skeleton (x 10), the eggs
are opaque and faintly tinted yellow. a. penis; b. stylet; c. male orifice; d. female orifice; e. oviduct; f. vagina; g.
spermatocyst; h. accessory female gland mass; i. hermaphrodite duct; j. ampulla; k. vas deferens (proximal, prostatic;
distal, muscular); 1. penial gland.
glands (Specimen No. 3). The liver system corresponds to
the simple papillar arrangement of the branchia. The
stomach could not be studied exactly. The jaw plate is
bilobed postero-dorsally, and the masticatory edge bears
a row of about 35 denticles (Specimen No. 2; see also
BERGH, 1874:93, pl. 2, fig. 7). The radular formula (Spec-
imen No. 2) is approximately 30 x 0.1.0. There are 4 or
5 slender denticles and some secondary ones on either side
of the median cusp, which is flanked by mirute serrations
(see also BERGH, 1874:93, pl. 2, figs. 10-12). All these
denticles and serrations serve to scrape completely the soft
flesh of the prey 7ubastraea out of its hard skeletal hol-
lows.
The genital organs of this species are similar to those
of Phestilla lugubris (RUDMAN, 1981:381, fig. 6). The con-
ical penis is armed with a short stylet (Specimens No. 2
and No. 3). The penial gland was found empty.
Anatomy of the specimen from Hawaii: This fully ma-
tured, dirty brown, preserved specimen (Figure 6) is filled
Page 246
The Veliger, Vol. 26, No. 4
Ym.
See
e
;
‘
:
; B
RY
'
Figure 6
Phestilla melanobranchia (orange form; Hawaii, 22 June 1967,
Harris coll.). A. preserved and contracted animal from dorsal
side, length 25 mm; B. right jaw plate (x 11); C. tooth (x 133).
a. genital orifices; b. nephroproct; c. anus; d. branchial papilla;
e. denticles on jaw edge.
internally with paired oral glands in the anterior half and
gonadal follicles in the posterior half of the body. Exter-
nally the branchial rows form prominent ridges (HARRIS,
1968:193; GOSLINER, 1980:49). There are 7 rows (or
ridges) in the right liver (and the partner on the left), and
10 rows in the left posterior liver on either side, the largest
rows consisting each of 15 or 16 papillae. The genital
orifices are found below the third branchial row of the
right liver.
The jaw edge has a row of blunt denticles. The radular
formula is 35 x 0.1.0. The slender denticles on either side
of the median cusp vary from 5 to 9 in number (the sec-
ondary denticles were not well marked). The median cusp
is provided laterally with 2 or 3 serrations which are ab-
sent in GOSLINER’s specimen (1980:fig. 7, A). The penis
was not examined (see the armed penis in GOSLINER, 1980:
fig. 7, C).
CONCLUSION
The genus Phestilla Bergh, 1874, represented by the type
species Phestilla melanobranchia was clearly shown to pos-
sess the digestive and genital organs characteristic of the
family Tergipedidae.
This genus is most closely allied to the so-called T7in-
chesia species group of Cuthona Alder & Hancock, 1855
(s.l.), in the external morphology with more or less simple
transverse rows of branchiae, and in the genitalia provided
with a penial stylet. However, Phestilla differs markedly
from Cuthona in the absence of the cnidosacs from the
branchiae and also in the formation of the greatly pecti-
nated radular teeth.
ACKNOWLEDGMENTS
I am indebted to Dr. Shiro Kawaguti (Japan) and Dr.
Larry G. Harris (USA) for making part of their collec-
tions of Phestilla available to me.
LITERATURE CITED
ALDER, J. & A. HANcock. 1855. A monograph of the British
nudibranchiate Mollusca. Ray Society, London. Pt. 7. Ap-
pendix: pp. 1-28.
BERGH, R. 1870. Malacologische Untersuchungen. In: C.
Semper, Reisen im Archipel der Philippinen. Wiss. Res.
2(1):1-30.
BERGH, R. 1874. Neue Nacktschnecken der Stidsee, malaco-
logische Untersuchungen. 2. J. Mus. Godeffroy 3(6):91-
116.
BERGH, R. 1905. Die Opisthobranchiata der Siboga-Expedi-
tion. Siboga-Exped. 50:1-248.
BERTSCH, H. & S. JOHNSON. 1981. Hawaiian nudibranchs.
Oriental Publ. Co.: Honolulu. 112 pp.
EDMONDSON, C. H. 1946. Reef and shore fauna of Hawaii.
Bernice P. Bishop Mus. Spec. Publ. 22:295 pp.
GosLINER, T. M. 1980. The systematics of the Aeolidacea
(Nudibranchia: Mollusca) of the Hawaiian Islands, with
descriptions of two new species. Pac. Sci. 33(1):37-77.
Harris, L. G. 1968. Notes on the biology and distribution of
the aeolid nudibranch (Gastropoda), Phestilla melanobran-
chia Bergh, 1874. Publ. Seto Mar. Biol. Lab. 16(3):193-
198.
Kawacutl, S. 1943. Notes on Phestilla sibogae with symbiotic
zooxanthellae. Taiwan Natur. Hist. Mag. 33(241):298-299.
(in Japanese)
Kay, A. E. 1979. Hawaiian marine shells. Reef and shore
fauna of Hawaii. Sect. 4: Mollusca. Bernice P. Bishop Mus.
Spec. Publ. 64(4):653 pp.
OSTERGAARD, J. M. 1955. Some opisthobranchiate Mollusca
from Hawaii. Pac. Sci. 9(2):110-136.
K. Baba, 1984
Risso-DOMINGUEZ, C. J. 1963. Measuring nudibranchs: a
standardization for descriptive purposes. Proc. Malacol. Soc.
Lond. 35(5):193-202.
RupMaN, W. B. 1981. Further studies on the anatomy and
ecology of opisthobranch molluscs feeding on the scleractin-
ian coral Porites. Zool. J. Linn. Soc. 71:373-412.
Page 247
RupMaN, W. B. 1982a. The taxonomy and biology of further
aeolidacean and arminacean nudibranch molluscs with sym-
biotic zooxanthellae. Zool. J. Linn. Soc. 74:147-196.
RuUDMAN, W. B. 1982b. A new species of Phestilla; the first
record of a corallivorous aeolid nudibranch from tropical
America. J. Zool. (Lond.) 198:465-471.
The Veliger 26(4):248-257 (April 2, 1984)
THE VELIGER
© CMS, Inc., 1984
Distributional Records for Terrestrial and Freshwater
Mollusca of the Cascade and Coast Ranges, Oregon!
by
BRANLEY ALLAN BRANSON anp ROGERS MacGOWAN BRANSON
Department of Biological Sciences, Eastern Kentucky University, Richmond, Kentucky 40475
Abstract.
Visitation of 125 Cascade and Coast mountain sites in Oregon during the summer of 1981
yielded records for 15 families, 29 genera, and 45 species of terrestrial and freshwater mollusks. Pisidium
insigne, Arion hortensis, Prophysaon foliolatum, and P. fasciatum are reported for the first time in Oregon,
an undescribed species of Hesperarion is discussed, and Trilobopsis loricata nortensis is reported in Oregon
for the first time since 1897.
INTRODUCTION
THE COAST AND CASCADE mountain ranges divide the
state of Oregon into two distinctive molluscan provinces,
a lush, moist and narrow western one (west of the Cascade
Crest) and a much wider, arid eastern one on the lee side
of the Cascade Crest. This general picture partially breaks
down along the Columbia River Gorge (DETLING, 1966;
LAWRENCE, 1939; LYNOTT, 1966) because Pacific coastal
vegetation extends eastward farther than otherwise pos-
sible, permitting several species of land snails to extend
their ranges eastward a few kilometers along the river.
For the most part, however, the bulk of the Oregonian
land-snail fauna occurs west of the mountains. The Co-
lumbia River itself also acts as a partial barrier, both to
dispersal and to genetic mingling. For example, in Wash-
ington, z.e., on the north side of the river, Oreohelix extends
westward along the Columbia River (B. A. BRANSON,
1977), whereas extensive searching on the south side of
the river has failed to disclose specimens.
Another relatively distinct botanical, and hence mollus-
can, region is the southwestern corner of Oregon. In this
area, northern Californian vegetation, including coastal
redwoods and tanoak, extends into Oregon, creating a
habitat that allows certain terrestrial mollusks to extend
their ranges northward for a short distance along the coast.
This article reports the results of field work conducted
in the Oregon components of the Coast and Cascade ranges
during the summer of 1981. It is an extension of work
commenced in Washington (B. A. BRANSON, 1977, 1980).
About 125 stations were visited in Oregon, although only
82 of these yielded molluscan specimens (see below). The
only previous systematic survey of Oregon terrestrial and
‘Supported by an Eastern Kentucky University Faculty Grant.
freshwater mollusks is that of HENDERSON (1929, 1936),
many of his records being reiterated by PiLsBry (1939,
1940, 1946, 1948).
LOCALITIES ano HABITATS
Much of the forest in the Coast Range has been repeatedly
and severely slashed and burned, creating very poor mol-
luscan habitats. Our work in these areas resulted princi-
pally in negative results. Likewise, practically none of our
collecting stations east of the Cascade Crest yielded spec-
imens. There is very little organic soil in that vast region,
most of the substrate being of volcanic origin and very dry
and porous. Lodgepole and ponderosa pines and other
drought-resistant plants are the typical vegetation. Al-
though we did not obtain mollusks at any of them, the
following sites are of interest because of biogeographical
importance, demonstrating the strong rain-shadow influ-
ence of the mountains: 8 sites along Oregon State Route
242 in McKenzie Pass, all in extremely dry, black, un-
consolidated lava; 6 sites along Century Drive, a 160-km
loop drive west of Bend, up to 1524 m elevation, mostly
in insect-devastated lodgepole pines; 6 sites at Paulina
Peak, a collapsed volcanic caldera southeast of Bend, mostly
in dry lava and pine forests; 8 sites along Oregon State
Route 58 east of the Cascade Crest, mostly in dry lava
and lodgepole pines; 5 sites around Diamond Lake north
of Crater Lake, mostly in dry lava and lodgepole pines;
and 10 sites equally distributed on Mount Mazama (Cra-
ter Lake National Park) from crest to foot, all in dry lava
and pines.
The winter and summer of 1980-1981 were among the
driest recorded (U.S. Weather Bureau, Portland, personal
communication). This doubtless played a role in reducing
our success in mollusk collecting. However, dead shells
B.
A. Branson & R. M. Branson, 1984
were not found in the localities delineated above, forcing
the conclusion that the Cascade Crest barrier is a real one.
The sites at which we successfully secured specimens
follow. The sites are numbered consecutively, and, in the
annotated list, specimens are referred to the sites from
which they were collected by these numbers. The figures
in parentheses represent the number of specimens secured.
The combination of letters and numbers given at each
collecting station below, z.e., R 23 E, T 35 S, S 31, are
map coordinates obtained from county maps.
1.
10.
ile
12.
NS),
14.
Chandler Wayside State Park and vicinity of Crooked Creek,
U.S. Route 395, R 23 E, T 35 S, S 31, Lake County; 1375
m elevation; western juniper, ponderosa pine, sparse under-
growth, dry lava substrate; 7 June 1981.
. Grizzly Peak, Fremont National Forest, 9.6 km east of SR
140 via Forestry Road 387, R 12 E, T 38 S, S 7, Lake
County; 1890 m elevation; Douglas fir, spruce, aspen, pines,
grass; light rain; rocks, soil, lava; 7 June 1981.
. Grasshopper Flat, Fremont National Forest, 3.2 km via SR
140 west of junction with Forestry Road 387, R 17 E, T 38
S, S 17, Lake County; 1516 m elevation; dry volcanic soil,
pines, firs; 8 June 1981.
. Bly Mountain Pass, Winema National Forest, 16 km north
of Bonanza, SR 140, R 11 E, T 37S, S 22, Klamath County;
1494 m elevation; dry volcanic soil, pine forest with evidence
of an old burn; 8 June 1981.
. Spence Mountain near Upper Klamath Lake, 13.6 km
northwest of Klamath Falls, SR 140, R 7 E, T 37 S, S 23,
Klamath County; 1391 m elevation; dry pine forest; 8 June
1981.
. Near Shake Camp Spring, Rogue River National Forest,
SR 140, 14.5 km west of Aspen Point, R 3 E, T 37S,S 5,
Jackson County; 1303 m elevation; spruce-fir forest, low
undergrowth and ferns; 8 June 1981.
. North Fork of Little Butte Creek and vicinity, SR 140, R
2 E, T 36 S, S 27, Jackson County; 571 m elevation; soil,
marginal oak forest; 8 June 1981.
. Coast Range, Siskiyou National Forest, 1.6 km northwest
of U.S. Route 199, R 8 W, T 37S, S 13, Josephine County;
457 m elevation; standing and downed oak trees, leaf litter;
9 June 1981.
. Coast Range, Siskiyou National Forest, U.S. Route 199 at
California border, R 9 W, T 41S, S 14, Josephine County;
366 m elevation; firs, salal, moss, rotting wood; 9 June 1981.
Coast Range, 1.2 km northeast of Brookings via North Bank
Road, R 12 W, T 39S, S 23, Curry County; 34 m elevation;
below burned over hill along Chetco River, bigleaf maple,
ferns, alder, salmonberry, Oregon myrtle (Umbellularia cal-
yfornica); 10 June 1981.
Coast Range, Siskiyou National Forest, 0.4 km northeast of
Loeb State Park, R 12 W, T 39 S, S 30, Curry County; 34
m elevation; coastal redwood, bigleaf maple, tanoak, alder,
fir, ferns, huckleberry, Oregon myrtle; 10 June 1981.
Low hillside, 1.9 km east of U.S. Route 101, Cape Sebastian
Overlook, R 14 W, T 37 S, S 31, Curry County; 230 m
elevation; tanoak, Oregon myrtle, fir, ferns, grass; 10 June
1981.
Humbug Mountain State Park, Siskiyou National Forest,
R 15 W, T 23 S, S 25, Curry County; 49 m elevation;
bigleaf maple, Douglas fir, tanoak, fir, ferns, moss; 11 June
1981.
Humbug Mountain State Park, Siskiyou National Forest,
R 15 W, T 33 S, S 25, Curry County; 183 m elevation,
other conditions as at Station 13; 12 June 1981.
3),
16.
18.
19.
20.
ile
Lid
23.
24.
25.
20.
lle
28.
29.
30.
31.
32.
33.
34.
Page 249
Humbug Mountain State Park, Siskiyou National Forest,
R 15 W, T 33, S 25, Curry County; 365 m elevation; other
conditions as at Station 13; 12 June 1981.
Humbug Mountain State Park, Siskiyou National Forest,
R 15 W, T 33 S, S 25, Curry County; 535 m elevation;
other conditions as at Station 13; 12 June 1981.
. Steep bluffs of the Middle Fork of the Coquille River and
in the river, 16 km east of Myrtle Point via SR 42, Coos
County; bigleaf maple, spruce, fir; 305 m elevation; 13 June
1981.
Bear Creek Recreation Area on Middle Fork of the Coquille
River and in the river, 43 km east of Myrtle Point via SR
42, Douglas County; 396 m elevation; Douglas fir, spruce;
13 June 1981.
Cape Arago at Sunset Bay, near sea level, Coos County;
Sitka spruce, skunk cabbage, salmonberry, ferns; 13 June
1981.
Honeyman State Park, R 21 W, T 19S, S 13, Lane County;
sea level; Sitka spruce, salal, bigleaf maple, wax myrtle,
alder; 14 June 1981.
Siuslaw National Forest, 4.8 km east of Florence via Canary
Road, R 10 W, T 19S, S 7, Lane County; 304 m elevation;
alder, ferns, decaying wood, skunk cabbage; 14 June 1981.
Siuslaw National Forest, 13 km east of Florence via SR
126, along Siuslaw River, R 10 W, T 18 S, S 7, Lane
County; 260 m elevation; Douglas fir, bigleaf maple, skunk
cabbage, decaying wood; 15 June 1981.
Siuslaw National Forest, 24 km east of Florence via SR
126, along Siuslaw River, R 9 W, T 18S, S 6, Lane County;
304 m elevation; Douglas fir, spruce, decaying wood; 15
June 1981.
Sea Lion Caves, R 11 W, T 16 S, S 3, Lane County; 213
m elevation; rocks, salal; 15 June 1981.
Cape Perpetua, Siuslaw National Forest campground along
Cape Creek and in creek, R 11 W, T 15 S, S 2, Lane
County; 183 m elevation; bigleaf maple, Sitka spruce, alder,
ferns, moss; 16 June 1981.
Cape Perpetua, Siuslaw National Forest Auto Loop Trail,
near summit, R 11 W, T 15 S, S 2, Lane County; 472 m
elevation; Sitka spruce, may apple, salal, ferns, moss; 16
June 1981.
Cape Perpetua, near the terminus of the Siuslaw National
Forest Auto Loop Trail, R 11 W, T 15S, S 2, Lane County;
670 m elevation; spruce, alder, salal, ferns, litter; 16 June
1981.
Cape Perpetua, “Devil’s Churn,” Siuslaw National Forest,
R 11 W, T 15S, S 2; 121 m elevation; Sitka spruce, salal;
16 June 1981.
Siuslaw National Forest along Alsea River, approximately
2.4 km east of Tidewater, via SR 34, R 10 W, T 13 S,S
20, Lincoln County; 290 m elevation; bigleaf maple, fir,
spruce, ferns, moss, alder; 17 June 1981.
Clear-cut forest, 17.7 km southwest of Corvallis, via SR 34,
R7W, T 13S, S$ 1, Benton County; 375 m elevation; young
Douglas fir and a few grasses; 17 June 1981.
South Beach State Park, R 11 W, T 11 S, S 19, 3.2 km
south of Newport, Lincoln County; 61 m elevation; salal,
rhododendron; 19 June 1981.
Devil’s Lake State Park, Devil’s Lake, R 11 W, T 6S, S
35, and in Devil’s River, Lincoln County; 64 m elevation;
Douglas fir, spruce, salal, ferns, skunk cabbage; 20 June
1981.
Swampy area, 1.8 km east of Lincoln City via West Devil’s
Lake Road, Lincoln County; Sitka spruce, ferns, skunk cab-
bage, decaying wood; 20 June 1981.
Cascade Head Experimental Forest, 4.0 km northeast of
Page 250
35),
36.
SHE
38.
39.
40.
41.
42.
43.
44,
45.
46.
47.
48.
49.
50.
Bile
SOE
22)
54.
Otis, R 10 W, T 6 S, S 14, Tillamook County; 335 m
elevation; Douglas fir, Sitka spruce, ferns, alder, moss, de-
caying wood, evidence of an old fire; 21 June 1981.
Neskowin Bay area, R 11 W, S 13, Tillamook County; 36.5
m elevation; grasses and sedges; 21 June 1981.
Cape Lookout State Park, R 10 W, T 2S, S 6, Tillamook
County; dead wood, Sitka spruce, skunk cabbage, ferns; 21
June 1981.
Jones Creek Forest Camp, 35 km east of Tillamook via SR
6, Tillamook County; 305 m elevation; clear-cut and burned
area, young Douglas fir; 22 June 1981.
Crest of Cape Lookout, R 10 W, T 2S, Tillamook County;
365 m elevation; decaying wood, Sitka spruce, moss, ferns;
22 June 1981.
Short Beach Trail, Oswald West State Park, Clatsop Coun-
ty; 152 m elevation; undisturbed Sitka spruce forest, western
redcedar, hemlock, ferns, moss; 23 June 1981.
Ecola State Park, Clatsop County; 183 m elevation; dis-
turbed Sitka spruce forest; 24 June 1981.
Fort Stevens State Park, Clatsop County; hardwoods, salal,
moss, ferns, Sitka spruce, alder; 24 June 1981.
Bradley Wayside, Clatsop State Forest, 6.4 km west of
Westport, old U.S. Route 30, Clatsop County; 180 m ele-
vation; wood sorrel, ferns, Douglas fir, decaying wood; 25
June 1981.
Low bluffs, 3.4 km west of Portland via U.S. Route 30,
Columbia County; 107 m elevation; volcanic rocks; 25 June
1981.
Latourell Falls and Latourell Creek, R 5 E, T 1 N, S 29,
Multnomah County; 61 m elevation; bigleaf maple, firs, moss,
volcanic rocks; 27 June 1981.
Wakkeena Falls and Creek, R 6 E, T 1 N, S 9, Multnomah
County; vegetation and edaphic conditions as at Station 44;
27 June 1981.
Horsetail Falls and Creek, R 6 E, T 1 N, S 9, Multnomah
County; vegetation and edaphic conditions as at Station 44;
27 June 1981.
Ainsworth State Park, R 6 E, T 1 N, S 3, Multnomah
County; pines, firs, bigleaf maple, alder, ferns, moss, vol-
canic rocks and soil; 27 June 1981.
Starvation Creek near Lancaster Falls, R 9 E, T1N, S 4,
Multnomah County; 33 m elevation; very dry volcanic soil
and rocks, pines, few alders along the creek; 28 June 1981.
Dry volcanic slope, 1.6 km below Mayer Roadside via In-
terstate 80N, R 12 E, T 2 N, S 11, Hood River County;
189 m elevation; ponderosa pine and volcanic rocks; 28 June
1981.
Mount Hood National Forest, Robinhood Campground, R
10 E, T 3 S, S 5, Hood River County; 1082 m elevation;
fir, pine, ferns, skunk cabbage; 28 June 1981.
Mount Hood, Mount Hood National Forest, 1.6 km above
Government Camp via Timberline Road, R 9 E, T 3 S,S
13, Clackamas County; 1372 m elevation; subalpine fir for-
est; 30 June 1981.
Mount Hood, Mount Hood National Forest, 4.8 km above
Government Camp via Timberline Road, R 8 E, T 3S, S
18, Clackamas County; 1524 m elevation; subalpine fir for-
est; 30 June 1981.
Still Creek Campground, Mount Hood National Forest, just
off U.S. Route 26 on Forestry Road S 32, R 9 E,T3S,S
18, Clackamas County; 1067 m elevation; pine, fir, ferns,
moss; 30 June 1981.
Old clear cut at Blue Box Pass, U.S. Route 26, R 9 E, T 4
S, S 20, Wasco County; 1227 m elevation; fir, spruce, much
decaying wood; 1 July 1981.
55.
56.
Die
58.
59),
60.
61.
62.
63.
64.
65.
66.
67.
68.
69.
70.
ae
72.
73.
The Veliger, Vol. 26, No. 4
Along Clear Fork of Sandy River, Mount Hood National
Forest Road N 12, R 8 E, T 2S, S 4, Clackamas County;
1042 m elevation; alder, penstemon, mountain mahogany,
fir, pine, very dry; 1 July 1981.
Along Hood River just outside Mount Hood National For-
est, Forestry Road N 18, R 9 E, T 1N, S 31, Multnomah
County; 613 m elevation; pine, Douglas fir, oak, grass, very
dry; 2 July 1981.
Along Hood River, 1.6 km downstream from Station 56,
Forestry Road N 18, R 9 E, T 1 N, S 31, Multnomah
County; 549 m elevation; alder, bigleaf maple, Douglas fir,
ferns, decaying logs; 2 July 1981.
Along Clackamas River, 4.0 km southwest of Ripplebrook
Ranger Station via SR 224, R 6 E, T 5S, S 27, Clackamas
County; 488 m elevation; Douglas fir, ferns, decaying wood;
3 July 1981.
Near Clackamas River, 3.2 km southwest of Ripplebrook
Ranger Station, SR 224, R 6 E, T 5S, S 34, Clackamas
County; 457 m elevation; dense shade, Douglas fir, ferns,
decaying logs; 3 July 1981.
Roaring River, SR 224, R 6 E, T 5 S, S 7, Clackamas
County; 304 m elevation; scouring rushes, decaying logs; 3
July 1981.
Near McNeil Forest Camp, Mount Hood National Forest,
6.4 km north of Zig Zag via Forest Road N 12, R 7% E, T
2S, S 9, Clackamas County; 496 m elevation; floodplain,
decaying logs; 3 July 1981.
Mount Hood Wilderness Area, Mount Hood National For-
est, 16 air km northeast of Zig Zag via Ramona Falls Trail,
R8E, T 258, S 24, Clackamas County; 1219 m elevation;
Douglas fir, redcedar, moss, ferns, decaying logs; 4 July
1981.
Whispering Falls, R 7 E, T 10S, S 19, Willamette National
Forest, Marion County; 610 m elevation; Douglas fir, hem-
lock, redcedar, ferns, moss, decaying wood; 5 July 1981.
Lost Prairie, U.S. Route 20, R 6 E, T 13 S, S 34, Linn
County; 1013 m elevation; fir-spruce forest; 5 July 1981.
Tombstone Pass summit, U.S. Route 20, R 6 E, T 13S,S8S
31, Linn County; 1291 m elevation; fir-spruce forest, decay-
ing logs, heavy snow cover; 5 July 1981.
Banks of Tumalo Creek, Tumalo State Park near Bend, R
10 E, T 18 S, S 8, Deschutes County; 977 m elevation;
willows, rank undergrowth, grass, volcanic soil; 7 July 1981.
North boundary of Three Sisters Wilderness, SR 242, R 7
E, T 15 S, S 34, Lane County; 1493 m elevation; firs, grass,
decaying logs, rocks; 8 July 1981.
Dead Horse Grade, north boundary of Three Sisters Wil-
derness, SR 242, R 7 E, T 15S, S 7, Lane County; 1189
m elevation; Douglas fir, spruce, decaying wood, grass; 8
July 1981.
Proxy Falls, Three Sisters Wilderness, R 7 E, T 16 8,8
23, Lane County; 975 m elevation; Douglas fir, vine maple,
redcedar, decaying logs; 8 July 1981.
Northwest boundary of the Mount Washington Wilderness,
off Forestry Road 2664, Willamette National Forest, R 5
E, T 14 S, S 33, Linn County; 1069 m elevation; lava,
Douglas fir, shrubs; 8 July 1981.
Salt Creek Falls, SR 58, Willamette National Forest, R 5%
E, T 22 S, S 33, Lane County; 1234 m elevation; redcedar,
ferns, Douglas fir, maple, decaying wood; 11 July 1981.
Montieth Rock area, SR 58, Willamette National Forest, R
4 E, T 21 S, S 27, Lane County; 670 m elevation; alder,
douglas fir, maple, redcedar, decaying wood; 11 July 1981.
West bank of Hills Creek Lake, R 3 E, T 22S, S 10, Lane
County; 472 m elevation; redcedar, fir, ferns, moss, oak,
Pacific madrone; 11 July 1981.
B. A. Branson & R. M. Branson, 1984
74. North bank of Willamette River between Sacandaga and
Indigo Springs, R 4 E, T 24 S, S 11, Forestry Road 21,
Willamette National Forest, Lane County; 792 m elevation;
redcedar, hemlock, Douglas fir, alder, maple, logging debris,
volcanic soil; 12 July 1981.
75. Near southwestern corner of Diamond Peak Wilderness at
end of Willamette National Forest Road 393 (off Forestry
Road 2154), 9.6 km above Emigrant Creek crossing, R 5 E,
T 24S, S 35, Lane County; 1372 m elevation; volcanic soil
and rocks, Douglas fir, white pine; 12 July 1981.
76. Emigrant Creek crossing of Willamette National Forest Road
21, R 5 E, T 24S, S 21, Lane County; 1115 m elevation;
Douglas fir, white pine, alder, maple, decaying wood; 12
July 1981.
77. Fall Creek Reservoir, R 1 W, T 19 S, Willamette National
Forest, Lane County; 335 m elevation; 12 July 1981.
78. Suzan Creek State Park, SR 138, banks of Umpqua River,
R 2 W, T 26 S, S 24, Douglas County; 285 m elevation;
Douglas fir, redcedar, alder, maple, oak; 13 July 1981.
79. Eagle Rock, banks of Umpqua River, SR 138, R 2 E, T
25% S, S 23, Douglas County; Douglas fir, cedar, alder,
maple; 14 July 1981.
80. White Horse Falls, SR 138, R 4 E, T 27S, S 2, Douglas
County; 1156 m elevation; white pine, Douglas fir, rocks;
14 July 1981.
81. Natural Bridge on Rogue River, Rogue River National For-
est Road 300, R 3 E, T 31S, S 16, Jackson County; 954
m elevation; Douglas fir, sugar pine, dry moss; 17 July
1981.
82. Three Horn Camp, Umpqua National Forest, SR 227, R
2 W, T 32 S, S 12, Douglas County; 790 m elevation;
Douglas fir, sugar pine, Oregon grapes; 17 July 1981.
ANNOTATED LIST or TAXA
In the list that follows, specimens are referred to collecting
sites by station number, and the number of individuals
collected at each site is given in parentheses. Unless oth-
erwise noted, all specimens are in the Eastern Kentucky
University Museum of Zoology (EKU).
BIVALVIA
SCHIZODONTA
UNIONIDAE
Margaritifera margaritifera falcata (Gould, 1850)
Collections: 17 (2), 23 (2).
Thriving populations of this bivalve were observed in
the Middle Fork of the Coquille River and the Siuslaw
River, but only four mature specimens were retained for
the EKU museum, all with purple nacre. A representative
measured 62.0 mm in length and 31.5 mm in greatest
depth.
HENDERSON (1929) reported this mussel as common in
many Oregon rivers, and Haas (1954) took several spec-
imens from the Rogue River at Grant’s Pass, Josephine
County.
Gonidea angulata (Lea, 1838)
Collections: 17 (4).
Four specimens from the Middle Fork of the Coquille
Page 251
River (Station 17) were retained for the EKU museum.
The species was previously reported from the Umpqua
and Silvies rivers (HENDERSON, 1929), the Rogue (HAAS,
1954), and the Walla Walla (COOPER, 1860).
HETERODONTA
SPHAERIIDAE
Sphaerium patella (Gould, 1850)
Collections: 17 (2).
This is one of the most widespread sphaeriids in the
Pacific northwest. HENDERSON (1929) reported the species
from several Oregon rivers and creeks.
Pisidium insigne Gabb, 1868
Collections: 32 (2).
These specimens, found on the muck bottom of Short
Creek running out of Devil’s Lake State Park, seem to fit
the characteristics of this species better than any other.
Pisidium insigne has not been previously reported from
Oregon.
GASTROPODA
MESOGASTROPODA
PLEUROCERIDAE
Most of the distributional knowledge of this family in
the Pacific Northwest is based upon the papers of
HENDERSON (1929, 1935a, b, 1936), B. A. BRANSON (1977,
1980), and B. A. BRANSON & BARRETT (1980). In the
last-cited paper, we discussed the possibility that
GOoDRICH (1942) was hasty in relegating HENDERSON’S
(1935a, b) species to the synonymy of Goniobasis silicula
and G. plicifera. Recently, BURCH (1982) and BURCH &
TOTTENHAM (1980) have elected to resurrect the generic
designation /uga to include all the western U.S. pleuro-
cerids, a name that is probably more in keeping with the
concept of subgenus. The nomenclatural problems asso-
ciated with the family Pleuroceridae should be referred to
the International Zoological Commission for decisions un-
der the plenary powers. The strict application of all the
changes recommended by BURCH (1982) and others would
result in much confusion. Therefore, we elect to utilize
the better known and more familiar designations of Good-
rich.
Goniobasis (Juga) coquillensis Goodrich, 1935
Collections: 17 (2), 18 (24).
From both sites, the specimens bear two to three rather
broad, purplish revolving bands, most obviously on the
body whorl and within the aperture. Otherwise, the basic
shell coloration is dark brown to mahogany. The sculp-
turing, spiral and axial, is very well developed. Most of
the apices have been eroded, only 4 to 5% whorls remain-
ing. A sample of 9 shells averaged 17.9 mm (15.5-21.0
mm) in height and 7.9 mm (7.0-9.0 mm) in greatest di-
ameter.
Page 252
Goniobasis (Juga) hemphilli dallesensis Henderson, 1935
Collections: 13 (2), 44 (4), 46 (4).
The specimens from Station 13, a small, clear creek at
the base of Humbug Mountain, are far out of range for
this race, but their characteristics are nearly identical to
those presented by HENDERSON (1935a, b), as confirmed
by comparison with topotypes. The spiral sculpture is
very faintly developed, whereas the remainder of the shell
is nearly smooth. There are two or three purplish bands
on the body whorl.
Goniobasis yrekaensis Henderson, 1935
Collections: 7 (27).
These dark mahogany-brown, slender shells are heavily
sculptured with radial and spiral lines, top to bottom. A
sample of 5 shells averaged 16.3 mm (15.0-17.5 mm) in
length, 6.7 mm (6.5-7.0 mm) in width, and had apertures
that averaged 6.9 mm (6.6-7.1 mm) by 4.5 mm. The
population in this stream is very large.
Goniobasis (Juga) silicula (Gould, 1847)
Collections: 25 (7), 77 (13).
All specimens were more or less typical in coloration
and sculpturing except for moderate banding at Station
aos
HYDROBIIDAE
The generic designation utilized herein is that of TAYLOR
(1966). BURCH (1982) utilized Fluminicola, as have many
other former authors.
Lithoglyphus virens (Lea, 1839)
Collections: 17 (2).
BASOMMATOPHORA
ANCYLOPLANORBIDAE
The family and generic designations used herein are
those of HUBENDICK (1978).
Planorbula (Menetus) opercularis (Gould, 1847)
Collections: 32 (2).
This is the dominant mollusk in the discharge creek at
Devil’s Lake.
PHYSIDAE
HENDERSON (1929, 1936) presented many records for
physid snails in Oregon but little has appeared in the
literature since then. BURCH (1982) and BuRCH &
TOTTENHAM (1980) use the generic epithet Physella rath-
er than Physa.
Physa gyrina ampullacea Gould, 1855
Collections: 7 (1), 32 (2).
BURCH (1982) and BURCH & TOTTENHAM (1980) re-
duced P. ampullacea to subspecific status.
Physa traski (Lea, 1864)
Collections: 1 (1).
The Veliger, Vol. 26, No. 4
A single specimen was retained for the record. How-
ever, the Crooked Creek population is a very large one.
No other mollusks were observed in the stream.
CARYCHIIDAE
Carychium occidentale Pilsbry, 1891
Collections: 17 (2), 29 (8), 47 (3), 77 (10).
Practically all these specimens were removed from
hardwood leaf litter. PILSBRY (1948) reported specimens
from Portland and Multnomah, Clackamas and Clatsop
counties, and HENDERSON (1929) took specimens from
Springfield Junction and reported (1936) upon specimens
at Stanford University from Astoria, Salem, and Portland.
A sample of seven individuals averaged 2.1 mm (2.0-2.2
mm) in length, 0.96 mm (0.8-1.0 mm) in greatest diam-
eter, and 5% (5%-5'%) whorls.
STYLOMMATOPHORA
HELMINTHOGLYPTIDAE
Monadema fidelis (Gray, 1834)
Collections: 8 (4), 10 (5), 11 (4), 13 (1), 15 (5), 16 (1),
17 (16), 18 (1), 19 (1), 23 (1), 44 (1), 48 (1), 49 (3), 73
(2), 74 (2), 77 (1), 78 (5), 81 (1), 82 (1).
The Columbia River gorge interrupts the Cascade Crest
weather barrier, allowing rain clouds to sweep moisture-
laden air masses farther inland than would be possible
otherwise, creating gradations of plant life (DETLING, 1966;
LAWRENCE, 1939; LYNOTT, 1966). There is a correspond-
ing color and banding variation in M. fidelis populations
distributed along the gorge (R. M. BRANSON, 1983). The
climatic amelioration, of course, allows this and other
species of snails and slugs to penetrate considerably far-
ther inland than elsewhere in the Cascade Mountain re-
gion.
Representative average measurements of adult shells
(z.e., with reflected peristomes fully formed) from the
principal biotopes follow: coastal (N = 16)—diameter: 31.7
mm (20.2-41.1 mm); height: 25.9 mm (18.0-39.0 mm);
whorls: 6+ (54-67%); Columbia River gorge (N = 2)—
diameter: 30.8 mm (28.2-33.5 mm); height: 19.2 mm
(16.5-22.0 mm); whorls: 512-6%; upland sites (N = 6)—
diameter: 30.3 mm (23.5-34.5 mm); height: 19.8 mm
(14.6-24.0 mm); whorls: 6% (5%4-6%). The largest spec-
imens were obtained from extreme southwestern Oregon
(vicinity of Harris Beach and Loeb State Park). However,
the coastal shells tend to have higher spires (Diameter/
Height ratio averages 1.4) than those from Columbia Riv-
er gorge or upland sites (D/H ratio averages 1.55).
Additional Oregon distribution records may be found
in PrusBry (1939), HENDERSON (1929, 1936), Haas
(1954), WALTON (1970), and ROTH (1981).
POLYGYRIDAE
Triodopsis germana (Gould, 1851)
Collections: 7 (5), 13 (1), 23 (1), 29 (1), 36 (1), 42 (1),
77 (1), 78 (8).
B. A. Branson & R. M. Branson, 1984
The specimens from Jackson County (Station 7) are
sparsely hirsute and, in general, match the diagnosis of 7.
germana vancouverinsulae (Pilsbry & Cooke, 1922)
(PitsBry, 1940). These specimens average 8.8 mm (8.5-
9.0 mm) in diameter, 5.3 mm (5.0-6.0 mm) in height,
and have 5-5% whorls. Specimens from coastal sites, by
contrast, bear many fine, close-set hairs. Many specimens
are only minutely perforate, and the parietal tooth is well-
developed; lip teeth are sometimes lacking. Shells from
coastal areas average 9.1 mm (7.7-11.0 mm), 6.3 mm
(5.5-7.5 mm) in height, and have 4%4-5'% whorls. Speci-
mens from inland sites, such as those from headwater
sections of the Umpqua River (Station 78), average some-
what larger, 11.6 mm (10.2-13.0 mm) in diameter, 7.4
mm (7.0-8.5 mm) in height, with 542-6 whorls.
Vespericola columbiana (Lea, 1838)
Collections: 6 (3), 10 (7), 12 (4), 13 (6), 15 (4), 16 (5),
17 (3),.19 (8), 20 (2), 21 (1), 22 (13), 23 (1), 24 (9), 27
CG)RZII Ae Sil) 33@)s 34:16)5 36); 37 a); 38 GB);
39 (1), 41 (8), 43 (1), 44 (11), 47 (2), 49 (1), 50 (3), 55
(3), 57 (1), 58 (1), 61 (1), 63 (1), 64 (1), 69 (1), 70 (1),
72 (4), 73 (1), 74 (4), 77 (2), 78 (5), 79 (2), 81 (3), 82
@).
This is one of the most widely distributed species of
land snails in the Pacific northwest (B. A. BRANSON, 1977,
1980; PitsBRy, 1940; HENDERSON, 1929, 1936), particu-
larly in Oregon west of the Cascade Crest. In Oregon, it
is also a rather variable species as one progresses inland,
although in the Coast Range and on the western slopes of
the Cascades most specimens are readily assignable to V.
columbiana pilosa (Henderson, 1928). Specimens from in-
land sites tend to be slightly larger in diameter. Average
measurements for mature shells secured along the coast
are: 13.7 mm (11.2-17.5 mm) in diameter, 9.2 mm (7.5-
11.5 mm) in height, with 512-6% whorls. A few of these
shells lack apertural teeth. At inland sites (Stations 55,
61, 73-74, 78-79) average measurements were: 16.0 mm
(14.0-18.0 mm) in diameter, 11.1 mm (10.0-12.2 mm)
in height, with 5%-6'% whorls. These latter shells tend
to be less hirsute than ones from coastal areas.
Specimens from the Columbia River gorge, from the
relatively dry habitats in Mount Hood National Forest
along the Hood River in Multnomah County, and from
sites along the Clackamas River in Clackamas County
differ considerably from those discussed above. Although
partially covered by a columellar reflection of the lip, the
umbilicus is obviously enlarged, 13-15% of the total di-
ameter of the shell. The reflected, white peristome is wide
and nearly flat, and the aperture, mostly because of the
angular periphery, has a shape reminiscent of that seen
in some depressed forms of Monadeniza, 1.e., it is elongated
horizontally. The matt shell surface bears very short, stiff
and sparse periostracal processes, spirally arranged on the
base. Average measurements of mature shells are: 16.5
mm (15.0-18.5 mm) in diameter, 11.1 mm (10.5-11.5
mm) in height, with 5%-6% whorls. This is probably the
Page 253
form PiLsBRy (1940) referred to V. columbiana latilabrum
Pilsbry, 1940. The marked differences in the shells sug-
gest that /atilabrum probably deserves full-species desig-
nation, but that will have to be verified by careful analysis
of the genital anatomy.
Trilobopsis loricata nortensis (Berry, 1933)
Collections: 10 (1).
Haas (1954) indicated that his collection of two speci-
mens from the redwoods west of the Hiouchi Bridge was
the first record for this subspecies since the original de-
scription. HENDERSON (1936) did not collect it but dis-
cussed ANDRUS’ (1897) report form Douglas County, Or-
egon, under the epithet 7. loricata loricata. PILSBRY (1940)
stated that he was “temporarily referring Andrus speci-
mens to 7. J. nortensis.” Thus, the single specimen re-
ported here appears to be the first verified report of the
species in Oregon since 1897.
The collecting locality is, of course, very similar to the
type locality in Del Norte County, California, including
the presence of Coast redwoods. The upper surface of the
shell bears strong spiral sculpture crossed by moderately
strong radial sculpture. The base is marked by well-de-
veloped spiral sculpture, and there is a plethora of raised,
crescent-shaped tubercles. There are two widely spaced
lip teeth and a relatively large, white and slightly sinuous
parietal tooth. T7rilobopsis loricata nortensis probably de-
serves full-species recognition, but this needs to be verified
by features of the soft anatomy.
HAPLOTREMATIDAE
Haplotrema vancouverensis (Lea, 1839)
Collections: 10 (3), 11 (2), 12 (7), 14 (4), 15 (3), 16
@); 7 (@), 22 (S), 23 @);, 25 @), 2 GD), 27 Oy ZL ©);
37 (1), 38 (5), 39 (2), 42 (2), 44 (1), 45 (2), 47 (4), 53
(1), 57 (1), 58 (1), 60 (1), 61 (1), 62 (2), 63 (3), 69 (1),
72 (4), 73 (1), 77 (2), 79 (2), 82 (1).
Haplotrema sportella (Gould, 1846)
Collections: 11 (2), 12 (1), 13 (11), 15 (7), 16 (1), 17
@), 19 Cl), Zl GD), Zz Ga), 248 @), 26 Gs 27 (i), ZB (©),
30 (3), 33 (2), 34 (2), 37 (1), 41 (10), 42 (2), 44 (16), 45
(7), 47 (6), 48 (1), 52 (2), 53 (1), 56 (1), 57 (4), 58 (1),
59 (2), 61 (2), 72 (4), 74 (6), 76 (2), 77 (2), 78 (1), 80
(2).
As stated previously (B. A. BRANSON, 1977), H. spor-
tella seems to be a complex of at least two species. The
whole west coast complex is in need of revision, utilizing
detailed anatomical features and, perhaps, the results of
electrophoretic analysis.
Specimens from Benton County, Oregon (Station 30)
are much greener than ones from most other localities,
and the shell is very solid, mostly because of a thick pearly
layer within.
Haplotrema sp.
Collections: 9 (2).
These shells, 19.0 mm in diameter, are palish green in
Page 254
color and are very smooth. The aperture is nearly trans-
verse. In general configuration, they are strongly reminis-
cent of H. keepi (Hemphill, 1890) from Redding in Shasta
County, California. Additional collecting at this locality,
which is at the California border, is required before spe-
cific diagnosis can be attempted.
ZONITIDAE
Representatives of six genera and nine species were
collected.
Euconulus fuluus (Miller, 1774)
Collections: 3 (4).
These shells measured 3.0—3.2 mm in diameter and had
5-5+ whorls.
Nesovitrea binneyana occidentalis (H. B. Baker, 1930)
Collections: 41 (3).
These specimens were living in hardwood leaf litter on
sandy soil.
Pristiloma cf. chersinella (Dall, 1886)
Collections: 17 (1).
The single waxen-white specimen, measuring 2.0 mm
in diameter with three whorls, seems closer to P. chersi-
nella than to any other Pristiloma. This species was pre-
viously reported from the vicinity of Upper Klamath Lake
in Oregon (BAKER, 1931; HENDERSON, 1936). However,
P. wascoense (Hemphill, 1911) is also known from Oregon
near Salem (BAKER, 1931) and the Wallowa Valley
(PILSBRY, 1946), although we were unable to recognize
that species in our collections.
Pristiloma lansing: (Bland, 1875)
Collections: 13 (1), 41 (4), 47 (2), 77 (5).
The imperforate shells are pale amber in coloration and
are transparent. Growth striae are nearly lacking. A very
low but well-developed denticulate ridge occurs immedi-
ately inside the aperture on the lower and middle lip. The
shells measure 2.0-2.5 mm in diameter and have 4%4-5%
whorls. PILSBRY (1946) and HENDERSON (1929) pre-
sented additional localities in Oregon.
Pristiloma johnsont (Dall, 1895)
Collections: 13 (1), 23 (1), 48 (1), 75 (1), 78 (1).
The last whorl in these waxen-white shells is nearly
twice as wide as the preceding one and the spire is strongly
depressed. Measurements: 2.4-2.8 mm in diameter, with
3¥%2 whorls.
Zonitoides arboreus (Say, 1816)
Collections: 74 (1), 78 (1).
Zonitoides arboreus is not a particularly common species
in the Pacific northwest, although it is apparently locally
abundant in the mountains farther east (B. A. BRANSON,
1977). The two specimens reported here measure 3.0—4.3
mm in diameter and have 34%2-4+ whorls.
Zonitoides nitidus (Miller, 1774)
Collections: 5 (1).
The Veliger, Vol. 26, No. 4
There are few records for this snail on the west coast.
In Oregon, it was known previously from Astoria (PILSBRY,
1946).
Striatura pugetensis (Dall, 1895)
Collections: 17 (1), 41 (2), 58(1).
There are few published records for this minute species
in Oregon. PILSBRY (1946) recorded it from Clackamas,
Clatsop, Klamath, and Multnomah counties, and
HENDERSON (1929, 1936) from Springfield and Elkhorn,
Oregon. Our specimens measured 1.2-1.6 mm in diame-
ter and were less than 0.5 mm in height; there are 2%4—
3% whorls.
Vitrina alaskana (Dall, 1905)
Collections: 1 (5), 2 (3), 7 (3), 66 (1).
All of our specimens were found east of the Cascade
Crest in very dry habitats, mostly under basaltic rocks.
All represent new distribution records within Oregon; the
previous reports are from Wallowa, Umatilla, and Kla-
math counties (PILSBRY, 1946), all of which are also dry
habitats.
TESTACELLIDAE
Testacella haliotidea Draparnaud, an agnathous shell-
bearing slug from western Europe (PILSBRY, 1946), was
reported from greenhouses in Clackamas County (BRUCE,
1950) and Salem and Corvallis, Oregon (HANNA, 1966).
ENDODONTIDAE
Punctum randolphi (Dall, 1895)
Collections: 66 (1).
This locality, a new distributional record in Oregon,
lies east of the Cascade Crest in very dry country. How-
ever, the specimen was removed from moist, decaying wood
on the banks of Tumalo Creek. All other published Or-
egon records are from west of the Cascade Crest (PILSBRY,
1948).
LIMACIDAE
In addition to the species reported here, PILsBRY (1948)
reported Limax maximus Linnaeus from Salem and Milax
gagates (Draparnaud) from Clackamas, Benton and
Douglas counties.
Deroceras reticulatum (Miller, 1774)
Collections: 7 (1), 66 (1).
Both individuals are more or less typical specimens, and
both were taken from areas with a history of recent human
disturbance. Several coastal and Columbia River sites were
given by PILsBRY (1948). This species is a rather serious
pest in Oregon strawberry and truck crops (CAPIZZI,
1960a) and grains (CApPIzz1, 1961).
Deroceras laeve (Miller, 1774)
Collections: 4 (5).
This site is a very dry pine forest near Klamath Lake,
a rather unusual habitat for this slug.
B. A. Branson & R. M. Branson, 1984
PUPILLIDAE
As pointed out many years ago (HENDERSON, 1929),
the family Pupillidae is rare to uncommon in the Pacific
northwest. Although we searched diligently in many hab-
itats at all elevations from sea level to the Cascade Crest
and at and above timberline on the high volcanoes, we
were unable to secure representatives of the family.
VALLONIIDAE
Vallonia cyclophorella Sterki, 1892
Collections: 1 (83), 3 (3), 4 (15).
Although a common species on the lee side of the moun-
tains, V. cyclophorella appears to be very scarce or even
lacking west of the Cascade Crest in Oregon. Measure-
ments: 2.7-3.0 mm in diameter; whorls 32-3 %.
ARIONIDAE
Although HANNA (1966) indicated that Arion fasciatus
Nilsson was common in the vicinity of Corvallis we did
not secure specimens in that area.
Arion ater (Linnaeus, 1758)
Collections: 19 (3), 20 (1), 21 (4), 31 (6), 32 (3), 35
(1), 36 (4), 41 (5), 47 (1).
These numbers are, of course, in no manner represen-
tative of population sizes. Whenever encountered, A. ater
was always present in enormous numbers, often at de-
structive levels, as also was reported by Capizzi (1960b).
At Stations 31 and 32, thousands of individuals per hect-
are were observed, principally at dusk and after sunset;
A. ater is principally a nocturnal slug (LEwIs, 1969). As
far as we can tell, REHDER (1947) was first to report this
European exotic from Oregon.
Arion hortensis (Férussac, 1819)
Collections: 32 (8), 41 (2).
This slug, another European exotic, apparently has not
heretofore been reported from Oregon. This diagnosis
should be substantiated.
Prophysaon andersoni (J. G. Cooper, 1872)
Collections: 9 (2), 13 (1), 15 (1), 17 (4), 18 (1), 19 (2),
25 (), 32 @)), SOQ), 4hl ©), Sl @), 52 Ch), 53@), 34
(2), 59 (1), 63 (4), 64 (2), 65 (3), 67 (4), 68 (1), 72 (2),
V7 QO), 73 @) 1 @), SO Gy
This handsome little slug is more widely distributed in
Oregon than any other member of the genus, often being
collected with P. caeruleum at 1500 m elevation or above.
A favored habitat is decaying logs and standing stumps.
Prophysaon foliolatum (Gould, 1851)
Collections: 14 (1), 42 (4).
These are the only published records for this slug from
Oregon. Although both collecting sites are worthy of note,
the Humbug Mountain station is of particular interest
because of its distance from the principal center of distri-
bution.
Page 255
Prophysaon caeruleum Cockerell, 1890
Collections: 59 (1), 60 (1), 63 (1), 75 (1), 76 (1), 81
Gi).
Known previously only from localities in Portland, Os-
wego, and Corvallis (PILSBRY, 1948), this bright-blue to
bluish-gray slug is one of formidable habitats. We took
specimens from high woodlands where the snow lingers
well into July. It is also one of the few slugs encountered
in dry, volcanic areas such as those at the Diamond Peak
Wilderness (Station 75) and the Rogue River National
Forest (Station 81).
Prophysaon dubium Cockerell, 1890
Collections: 7 (1).
In life, this specimen was dark bluish-gray above, and
the narrow, rugose, undivided sole was grayish-white. The
mantle, the same color as the body with three indistinct,
blackish, chevron-like marks at the anterior end, is smooth
above, but bears very small papillae on the sides. The
body tapers posteriad, and bears deep, longitudinal grooves;
shallow, transverse grooves periodically cut across the lon-
gitudinal ones. There is no mucous pore. Preserved mea-
surements are: total length—16.0 mm; mantle length—
6.0 mm.
The only previous records for the species in Oregon are
from Portland, Oswego, and Corvallis (PILsBRy, 1948),
and “Oregon” (WEBB, 1961).
Prophysaon vanattae Pilsbry, 1948
Collections: 50 (2), 52 (2), 57 (3), 59 (1), 61 (8).
Apparently restricted in distribution to northwestern
Oregon and Washington, this slug is often confused with
P. fasciatum. The red phase discussed by PILSBRY (1948)
and B. A. BRANSON (1980) is rare to lacking in most of
the Oregon range, most of the specimens being similar to
those from the Olympic Peninsula (B. A. BRANSON, 1977).
Individuals from the population on and near Mount Hood
are often nearly black, other color-pattern elements being
obscured.
Prophysaon fasciatum Cockerell, 1890
Collections: 44 (1), 62 (1).
These two specimens are of the kind referred to as P.
f. obscurum Cockerell by PILsBry (1948), who stated that
the northern race (Washington) was probably a distinct
species, based upon genital differences. These are the first
published records for Oregon.
Hesperarion species
Collections: 38 (2).
Prior to this report, the genus Hesperarion was thought
to be restricted in distribution to California around and
south of San Francisco (GREGG, 1961; MEAD, 1943;
PitsBry, 1948) and Tehama County (LANGE, 1944). Our
record represents a significant range extension for the ge-
nus.
This apparently unknown slug species differs from all
other members of the genus Hesperarion by characters of
the genitalia and features of the body sculpturing on the
Page 256
head and body, by the raised hump-like area beneath the
mantle, and by color pattern. It is most closely related to
H. hemphilli (W. G. Binney) but differs from that species
in the decidedly reddish pigmentation, in having the black
spots of the body arranged in a definite pattern and rows,
in having a larger caudal pit with a down-turned ventral
portion, and in possessing a massive triangular and con-
stricted penis. Additional differentiating features will
probably be discovered in the radula, genitalia, and mus-
culature when additional specimens become available. A
voucher specimen was deposited at the Field Museum of
Natural History (FMNH 198763) in Chicago.
Hemphillia malone: (Pilsbry, 1917)
Collections: 42 (2), 51 (1), 53 (9).
This species appears to be restricted to the Columbia
River gorge and Mount Hood regions of Oregon. Previous
distribution records (Clackamas, Multnomah, and Hood
River counties) were given by KOZLOFF & VANCE (1958).
Hemphill cf. burringtoni (Pilsbry, 1948)
Collections: 39 (1 immature).
This specimen is indistinguishable from specimens se-
cured from the Olympic Peninsula. However, the area
needs to be more thoroughly searched for mature speci-
mens before this species is definitely added to the Oregon
fauna.
Ariolimax columbianus (Gould, 1851)
Collections: 10 (1), 13 (2), 16 (1), 17 (2), 18 (1), 19
@), 2D ()), 21 ©), 2 ©), 23 Cl), 24 @), ZS @), 2 GW),
23 (CU); 2 @), Ch), dil @), 34 @), 35 @)), 36 CG), 3s
(2), 39 (1), 40 (1), 42 (4), 44 (1), 45 (1), 47 (1), 48 (1),
62 Gl), 63 @), 70 GD); 7 @), 7 @), 76 @, 77 Ms Ve
(3).
Although both maculated and spotless color morphs oc-
cur throughout the range of this widespread slug, Ore-
gonian populations appear to be less variable than those
farther north in Washington and on the Olympic Penin-
sula (B. A. BRANSON, 1977). MEAD (1943) provided a
detailed discussion of the genus Ariolimax.
ACKNOWLEDGMENTS
We greatly appreciate the fine cooperation and assistance
of Mr. Mark E. Forbes, Resource Management Special-
ist, during our collecting attempts at Crater Lake Nation-
al Park. Mr. T. Edwin Cummings, Staff Fish Biologist,
Department of Fish and Wildlife, Portland, Oregon, pro-
vided us with instructions regarding state regulations, and
Mr. Tony Skufca, Director of Recreation, Region 6, U.S.
Forest Service, Portland, Oregon, provided us permission
for our work in his district. Finally, Mary Louise Bran-
son, wife of the senior author, accompanied us throughout
the entire excursion.
LITERATURE CITED
ANpRuS, F. H. 1897. Notes on the land shells of Douglas
County, Oregon. Oregon Natur. 4:53-54.
The Veliger, Vol. 26, No. 4
Baker, H. B. 1931. Nearctic vitreine land snails. Proc. Acad.
Natur. Sci. Phila. 83:85-117.
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lamette Valley, Oregon. Coop. Econ. Insect Rep. 10:466.
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The Veliger 26(4):258-263 (April 2, 1984)
THE VELIGER
© CMS, Inc., 1984
The Biology of the Northeastern Pacific Turridae. IV.
Shell Morphology and Sexual Dimorphism in
Aforia circinata (Dall, 1873)
by
RONALD L. SHIMEK'!
Friday Harbor Laboratories, Friday Harbor, Washington 98250
Abstract.
The shell morphology of the boreal deep-water species Aforia circinata is examined, and
a pronounced dimorphism in sexually mature animals is described. Mature females have a canal-like
notch, which is lacking in males, midway down the outer lip. The notch is similar to, but smaller than
the siphonal canal, and arises abruptly from a low ridge at an approximate shell length of 76 mm. The
notch may function as an auxiliary siphonal canal during oviposition. No other sexual differences in
shell shape of immature animals could be demonstrated, although small males are more variable in
some measurements than are small females, or large animals of either sex. Healed shell fractures are
common, and are probably due to attempted predation by crabs.
INTRODUCTION
WITH THE EXCEPTION of the cephalopods, sexual dimor-
phism has not been commonly demonstrated in mollusks.
In prosobranch gastropods, sexually determined size di-
morphisms have been reported in several lineages: for Cyy-
praecassis (CLENCH & ABBOTT, 1943); Fasciolaria (WELLS,
1970); Mitra (CHESS & ROSENTHAL, 1971); Thala (MAES
& RAEIHLE, 1975); Neptunea (MACINTOSH & PAUL, 1977);
Buccinum (TEN HALLERS-TJABBES, 1979); and Drillia,
Strictispira, Pilsbryspira (MAES, 1983). That females are
larger than males within the stenoglossa may be a general
trend that goes unnoticed due to the relatively large sam-
ple sizes needed to determine a statistically significant dif-
ference in the mean adult size between the sexes of any
given population. Although Mags (1983) demonstrated
size differences in four species of Caribbean turrids, no
size differences have been observed in any northeastern
Pacific turrids examined to date (SHIMEK, 1983a, b, c),
even though sufficiently large samples have been exam-
ined in detail.
Sexually correlated differences in shape are even less
common. The sexes of Voluta musica Linné, 1758, and
Voluta ebraea Linné, 1758, are sufficiently different to be
easily distinguished (CLENCH & TURNER, 1964), but
whereas there are slight sexual differences in the shell
‘ Mailing address: Bamfield Marine Station, Bamfield, British
Columbia VOR 1B0, Canada.
shapes of Buccinum undatum, sophisticated mathematical
and measuring techniques are needed to demonstrate them
(TEN HALLERS-TJABES, 1979). Neptunea species also have
a size dimorphism similar to that shown in Buccinum un-
datum (MacINTOSH & PAUL, 1977) and similar subtle
shape differences may occur. Sexual shell-shape differ-
ences have not been reported in the toxoglossa, although
“odd” shapes at variance to the typical shell shape have
been noted for several tropical turrids (POWELL, 1964,
1969).
The northeastern Pacific boreal turrid Aforia circinata
(Dall, 1873) is seldom collected, and ecologically poorly
known; data on diet, habitat, reproduction, and popula-
tion biology are lacking. During examination of specimens
of this species, several individuals were found exhibiting
the “odd” shape (Figure 1) described and figured by
POWELL, 1969. I attempted to correlate this shape with
other observable features of the organisms.
A characteristic of the immense prosobranch family
Turridae is the presence of a secondary or anal notch.
The position of this notch varies with the subfamily of
turrids examined, but it is typically very near the shoul-
der. It never forms a “spout” nor has a siphonal canal-
like appearance.
The hypothesis tested was that the odd shape, a distinct
notching of the outer lip, similar in shape to
the siphonal canal, is randomly distributed throughout the
species. The tertiary notch might be related to sex and/
>
“tertiary
or size (and presumably age).
R. L. Shimek, 1984 Page 259
Figure 1
Aforia circinata. Scale bars = 1 cm. A. Mature male. B. Mature female; note tertiary notch on outer lip (compare
with Figures 1A and 1E). C. Mature female (different from the one illustrated in Figure 1B); arrow indicates
initiation of notch; note healed fractures, and how the notch is displaced after subsequent break. D. Immature
male. E. Immature female; material on shell (arrow) is the remains of a hydractiniad hydrozoan; virtually all
shells were covered with this material, and it had to be removed with the underlying periostracum to examine the
shell. F. Mature male with a low ridge (arrow); females often had similar, albeit more pronounced ridges.
Page 260
Figure 2
Measurements of Aforia circinata. L, shell length; W, shell width;
Ap L, aperture length; D, distance from the shoulder carina;
We, width of the siphonal canal; Wn, width of the tertiary notch;
Hn, height of the tertiary notch.
MATERIALS anpD METHODS
The specimens of Aforza circinata examined were collected
from two localities in the Bering Sea, 59°20.3'N,
173°44.3'W, and 58°21.2'’N, 172°19.0'W, with a 400-mesh
Eastern Otter Trawl; thus, no specimens less than 50 mm
long were collected. The first site, at a depth of 109 m,
sampled on 25 June 1980, yielded 30 specimens; the sec-
ond, at a depth of 102 m, sampled on 23 June 1980,
provided seven specimens. The animals were preserved
immediately in 95% ethanol. Animals from both popula-
tions were pooled for all analyses.
During examination, the snail’s body was removed from
the shell, the sex was determined, and an arbitrary esti-
mate of maturity was obtained by examining the second-
ary sexual organs. In mature males, the penis is large, at
least twice as long as the width of the mantle cavity. Males
were classified as immature if the penis length was less
than or equal to mantle-cavity width at the base of the
penis. In mature females, the capsule gland is large and
robust; generally it is three to five times the diameter of
the nearby hindgut. Consequently, females were classified
as immature if the capsule gland was the same diameter
or smaller than the nearby hindgut.
The Veliger, Vol. 26, No. 4
ZIaQ2mr-
Figure 3
Size-frequency distribution of the Aforia circinata examined.
Length in mm.
The entire gut was dissected out, placed in a Petri dish
of water, and opened to determine the contents. Two of
the 37 animals examined were too badly fractured to be
used for shell analysis, but their gut contents were ex-
amined.
The shell shape was noted, particularly the presence or
absence of a tertiary notch. Additionally, the number of
major healed fractures on the anterior three whorls was
determined. On some individuals, the outer aperture lip
and portions of the body whorl were badly fractured dur-
ing collection; hence, the number of healed fractures could
not be determined. The total shell length, the width, and
the aperture length were measured. If a notch was pres-
ent, its height and width were measured and its position
relative to the center of the major shoulder carina was
determined. The width of the siphonal canal at its nar-
rowest point was also measured (Figure 2). All measure-
ments were made with dial calipers to 0.1 mm.
The shell measurements were transformed into their
natural logarithms for the purpose of comparing mea-
surements, for determining differences between the snail
categories of large, small, males and females, and for com-
paring length-to-width regressions.
The pooled samples were examined by comparing (1)
the natural logarithm of the shell length to the natural
logarithm of the shell width, (2) the presence or absence
of the notch, and (3) the variance of the ratio of natural
logarithm of shell width to the natural logarithm of shell
length between and within each sex. Within-sex compar-
isons were based on size differences, animals less than or
equal to 70.0 mm being designated “‘small,”’ whereas those
in excess of 70.0 mm were designated large. Examination
indicated sexually mature animals always exceeded 70.0
mm in shell length.
R. L. Shimek, 1984
Page 261
Table 1
Shell characteristics of Aforia circinata. / = Shell fractured; thus, the number of healed fractures is undetermined.
Shell measurements (mm)
Mean:
Aperture Tertiary
Length Width length notch
Females
53.1 20.0 31.2 =
54.2 20.3 31.2 =
54.9 20.4 34.0 =
58.4 23.3 2 =
61.9 23.5 33.6 ridge
63.1 23.1 38.3 =
64.6 DBWO) 37.4 =
69.1 26.3 40.5 =
71.5 26.7 36.0 =
72.3 25.8 43.9 ridge
125) 28.0 42.4 ridge
76.2 30.9 40.4 +
Wes 28.0 42.4 +
78.5 28.9 46.2 +
82.3 30.1 48.7 ridge
85.2 32.0 50.6 +
87.7 32.4 54.6 ridge
88.2 31.2 49.4 +
Males
52.6 18.6 S39) =
54.7 DIES 30.6 =
58.6 21.4 35.0 =
59.3) 22.6 27.6 =
66.0 23.1 BES =
72.3 26.0 44.1 =
74.1 27.8 43.4 =
75.6 Dies 43.4 =
75.8 26.8 46.8 =
80.2 26.9 45.0 =
80.5 26.9 26.9 ridge
81.8 31.9 50.2 =
82.2 31.8 50.1 ridge
84.3 30.4 49.0 =
85.4 35.7 52.4 =
85.7 32.7 51.2 =
86.0 32.1 49.5 =
RESULTS
The results are unambiguous: no males have a pro-
nounced notch, and no females smaller than 70 mm have
one. All of the females that had notches were sexually
mature (Table 1). Not all females have the pronounced
notch, but all over 70 mm in length have either the notch
or a distinct low ridge. On most of those animals with the
notch, the ridge can be demonstrated at younger positions
on the body whorl. Some males have a similar low ridge,
albeit not as pronounced as the ridge in females. Typi-
cally, the notch arises abruptly from the ridge when the
Healed fractures
Body Mean number
whorl per whorl
H wWHouUuaprn Pr A WO ANN On™
rex)
rex)
49+ 1.9 2s) as (09) (N = 11)
I+ WN UN ON W BX A AW OnWnX™
Ww
=)
o>
uN
ileil (N = 11)
animal is about 76 mm long, and generally does not be-
come more pronounced as the animal gets older. The notch
is a hollow fold in the outer lip and is substantially smaller
in all dimensions than the siphonal canal, which it super-
ficially resembles (Table 2). Some males have a low ridge
similar to the low ridge found on the smaller females,
albeit not as pronounced (Figure 1).
The allometric relationship of shell width to shell shape
for all Aforia was In W = 0.98 In L — 0.92. The trans-
formed length-versus-width relationships were fitted by
linear regressions and, with the exception of small males,
no significant differences were found between the allo-
Page 262
The Veliger, Vol. 26, No. 4
Table 2
Characteristics of the tertiary notch. All measurements in mm.
Distance from
shoulder carina Width
AVI low ridge
16.3 low ridge
18.9 LBZ
V2 low ridge
19.6 3.07
19.3 1.76
16.1 2.64
14.0 low ridge
18.8 low ridge
13.8 low ridge
Hod low ridge
20.9 3.16
Mean values (+1 SD)
X: Wh. d2 22 2.61 + 1.01
N: 12 5
metric relationships of length to width between any of the
subgroups. The large variance in the shell length-to-width
ratio and the small sample size of the immature male
group casts some doubt on the real significance of the
difference. ANOVA on the In width/In length ratio re-
vealed significant differences between large and small an-
imals caused by the large variances within the group of
small males examined.
Healed major shell fractures (determined as shell frac-
tures after which the pattern of spiral sculpture was al-
tered) were common in these animals, but were not sig-
nificantly more numerous in one sex. The body whorl
often has more healed shell fractures than either of the
next two posterior whorls (Table 1); however, this is
probably a function of the relative size of the body whorl.
Per unit area of shell surface, no trend is apparent.
The size-frequency distribution of these pooled samples
indicates no apparent differences in the male and female
components. Neither sex predominates in either the large
or the small size ranges (Figure 3).
No identifiable gut contents were seen in any of the
specimens; in two cases, however, sand was in the hindgut.
DISCUSSION
The hypothesis that the notch is randomly distributed
throughout the species is clearly disproven. The tertiary
notch of Aforia circinata is pronounced only in mature
females. Those adult females lacking a pronounced notch
have a distinct ridge, lacking in most males.
The function of the tertiary notch remains unknown,
although its predominance in females suggests a possible
copulatory or oviposition role. MACNIEL (1960) suggested
the presence of a similar notch in the deep-water turrid
Tertiary notch
* = Males; all others females.
Shell length
Siphonal canal when notch
2.1/3 26 Oe)
Height Width first evident
4.39 70.3
5.82 V3
3.86 4.16 74.2
4.96 74.8
2.40 5.68 76.4
4.76 4.62 77.4
3.46 5.47 80.0
5.54 80.0*
5.82 82.0
3.93 fractured
5.17 fractured
4.18 fractured fractured
5.05 + 0.68 76.4 + 3.9
11 9
Pinguigemmula might be correlated with oxygen lack and
thus might function as a secondary siphonal canal. In
Aforia, the notch may similarly function as a subsidiary
canal allowing the female to shift siphonal position to
ensure an adequate flow of oxygenated water while ovi-
positing the tough egg capsule characteristic of turrids.
POWELL (1964, 1969) dismissed MacNiel’s suggestion
based on the callus-filled nature of some of the notches
found in the deep-water tropical turrids, a condition ab-
sent in Aforza. If the function hypothesized here is correct,
the notch might be expected in species from habitats where
environmental conditions would select for accessory struc-
tures to facilitate increased oxygen flow during oviposi-
tion. POWELL (1964, 1969) stated similar notches are found
in a few individuals of some deep-water tropical turrids:
Ptychosyrinx, Epidrella, and Gemmula hombron: (Hedley,
1922). As Aforia is also from deep water, perhaps the
notches form a common solution to some problem inherent
in oviposition or copulation in deep-water habitats.
Both sexes have a large number of healed shell frac-
tures, indicating unsuccessful attempts by shell fracturing
predators, presumably crabs. There was no significant dif-
ference in the number of healed shell fractures between
the sexes, and the relatively even sex ratio further argues
for no differential predation. Paralithodes camtschatica
(Tilesius, 1815), Chionecetes opilio O. Fabricius, and C.
bairdi Rathbun, 1893, are found nearby in large numbers.
Paralithodes, the Alaskan King Crab, probably has the
ability to attack and break the shells of Aforza, although
it has not been demonstrated to do so.
Aforia has a long and relatively well-documented fossil
record (JAVIDPOUR, 1973). Similar low ridges are seen on
illustrations of several of the fossil species illustrated by
JAvippour (1973): Aforia addicotts Javidpour, 1973; A.
R. L. Shimek, 1984
campbelli Durham, 1944; A. clallamensis (Weaver, 1916)
and A. tricarinata Addicott, 1966. Indeed, one species, A.
tricarinata, appears to be distinguished by the presence of
just such a ridge, along with two shoulder carina. The
specimens of A. addicotti and A. clallamensis figured by
JAVIDPOUR (1973; figs. 12, 13) are particularly similar to
A. circinata (Figure 1). It is unclear whether specimens
without the ridge were collected in the same formations.
If so, the sexual nature of the ridge, and subsequent notch,
casts doubt upon the validity of these species in particular,
and other species of Aforza described using a secondary
sub-shoulder ridge as a primary characteristic.
A thorough examination of collections containing tur-
rids from the appropriate habitats should determine how
widespread the phenomenon of a tertiary notch is. If this
rather peculiar shape is recognized as a normal sexual
variant of shell shape and reported, then not only will
data on sexual ratios of mature populations become avail-
able, but an estimate of the adaptive plasticity of the shell
morphology could be obtained.
ACKNOWLEDGMENTS
I thank Mr. Paul A. Raymore, Jr., of the National Ma-
rine Fisheries Service (NOAA) for collecting the speci-
mens of Aforia used in this study. The facilities of the
University of Washington Friday Harbor Laboratories
were used with the permission of the director, Dr. A. O.
D. Willows. Earlier drafts of this paper were read by R.
Fredrickson and two anonymous reviewers, who made
many useful suggestions.
LITERATURE CITED
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biology of Mitra idae. Veliger 14(2):172-176.
CLENCH, W. J. & R. T. ABpoTr. 1941. The genera Cyrae-
cassus, Morum, Sconsia, and Dalium in the Western Atlantic.
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MacNieL, F. S. 1960. Tertiary and Quaternary Gastropoda
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Islands. Bull. Mar. Sci. 33:305-335.
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The Veliger 26(4):264-273 (April 2, 1984)
THE VELIGER
© CMS, Inc., 1984
Distribution and Radular Morphology of Various
Nudibranchs (Gastropoda: Opisthobranchia)
from the Gulf of California, Mexico
HANS BERTSCH!'
Instituto de Investigaciones Oceanologicas, Universidad Autonoma de Baja California,
Apartado Postal 453, Ensenada, B.C., Mexico
ALEX KERSTITCH
Department of Ecology and Evolutionary Biology,
University of Arizona, Tucson, Arizona 85721
Abstract. We report new distribution records for 14 species of nudibranchs from the tropical eastern
Pacific faunal region. We present scanning electron micrographs of the radulae of Chromodoris annulata,
Histiomena convolvula, and Flabellina cynara, and document the gorgonian prey of H. convolvula.
DURING THE PAST five years, we have made numerous
scuba diving research trips throughout the Gulf of Cali-
fornia. We have found specimens of opisthobranchs that
constitute significant new distributional records for the
tropical eastern Pacific faunal region (Panamic province).
In this paper we report new range records of 14 species
of nudibranchs, present scanning electron micrographs of
the radulae of three species, and document the prey of the
arminid Histiomena convolvula. We carefully distinguish
disjunct occurrences: that is, species reported from differ-
ent zoogeographical marine faunal provinces that have
large gaps in their known distributional ranges.
The latitude and longitude of our collecting localities
are given in Table 1, and their locations are indicated on
the map (Figure 16).
DORIDOIDA
PHANEROBRANCHIA
GONIODORIDIDAE
Trapania sp.
This specimen resembles the southern Californian 77a-
pama velox (Cockerell, 1901). However, its color pattern
‘Mailing address: 4444 W. Pt. Loma Blvd., #83, San Diego,
CA 92107.
is distinct enough to warrant not immediately identifying
this single specimen to the species level.
The body is white (Figures 1 and 2), with distinct choc-
olate-brown streaks and patches. These markings are very
pronounced, clear, and sharply margined. The tips of the
cephalic tentacles, rhinophores, gills, and lateral extra-
branchial appendages, and the posterior extreme of the
foot are a brilliant yellow.
(1) 1 specimen (20.2 mm long), subtidal, 4.5 m deep,
Cabo San Lucas, Baja California Sur; leg. Alex Kerstitch
(AK), 20 July 1981.
Specimens of this species have recently been reported
from Isla Cedros and Bahia Vizcaino (BEHRENS, 1983).
CRYPTOBRANCHIA
CHROMODORIDIDAE
Chromodoris annulata Eliot, 1904
Known collecting records of Chromodoris annulata have
been confined to the western Indian Ocean: from the Red
Sea (GOHAR & ABOUL-ELA, 1957; ABOUL-ELA, 1959);
Diani, Kenya (RUDMAN, 1973:189-190); Zanzibar and
Dar es Salaam, Tanzania (ELIOT, 1904:389-390;
EpMuNDS, 1971:371-372); and Natal, South Africa
(BARNARD, 1927).
The following specimen represents the first collecting
H. Bertsch & A. Kerstitch, 1984
Page 265
Table 1
Latitude and longitude of Mexican collecting localities.
Pacific coast of Baja California
Islas Coronados, B.C.
Ensenada, B.C.
Isla San Martin, B.C.
Bahia San Quintin, B.C.
Isla Guadalupe, B.C.
El Tomatal, B.C.
Isla San Benitos
Isla Cedros
Bahia Vizcaino
Punta Santo Domingo, B.C.S.
Gulf of California, western shore
Consag Rock, B.C.
San Felipe, B.C.
Puertecitos, B.C.
Bahia de los Angeles, B.C.
Isla Tortuga, B.C.
Loreto, B.C.S.
La Paz, B.C.S.
Bahia Las Cruces, B.C.S.
Cabo San Lucas, B.C.S.
Gulf of California, eastern shore
Puerto Penasco, Sonora
Bahia Kino, Sonora
Morro Colorado, Sonora
Bahia San Carlos, Sonora
Guaymas, Sonora
Mazatlan, Sinaloa
32°25'N; 117°15’W
31°51'N; 116°38’W
30°31'N; 116°10’W
30°24'N; 115°53’W
29°00'N; 118°20’W
28°29'N; 114°04'W
28°20'N; 115°40’W
28°07'N; 115°11’W
27°50'N; 114°51'W
26°19'N; 112°40’W
31°07'N; 114°29'W
31°01'N; 114°49’'W
30°21'N; 114°38’W
28°57'N; 113°31’W
27°27'N; 111°58’W
26°01’N; 111°20’W
24°13'N; 110°25’'W
24°13'N; 110°05’W
22°52'N; 109°55'W
31°18'N; 113°32’W
28°49'N; 111°59’W
27°58'N; 111°22’W
27°56'N; 111°08’W
27°55'N; 110°54’W
23°11'N; 106°25’W
Pacific coast of mainland Mexico
21°20'N; 105°15'W
19°12'N; 104°43’W
19°03'N; 104°19’W
Sayulita, Nayarit
Melaque, Jalisco
Santiago Bay, Colima
data of Chromodoris annulata from the eastern Pacific
Ocean, and from anywhere outside the Indian Ocean:
(1) 1 specimen, subtidal, 9 m, Isla Tortuga, Baja Cal-
ifornia; /eg. AK, 4 April 1980.
Identification of this distinctive species is unmistakable:
white body with yellow spots, dark purple margin around
the mantle, and a dark purple ring around the gills with
another dark purple ring enclosing both rhinophores (Fig-
ure 3).
Morphology of the radula (Figures 4 to 7) further con-
firms the identification. The drawings of EDMUNDs (1971:
317, fig. 15E) are nearly identical with the tooth shapes
of our specimen from the Gulf of California. The small
denticles are located on the lateral outer sides of each
tooth, with a shift in position to the posterior surface of
the outermost teeth. The present specimen had a radular
formula of 56-58 (45-49.1.45-49). The combined radu-
lar formula of the 5 known specimens is: 58-75 (42-
59.1.42-59). Table 2 gives the numbers of tooth rows and
teeth per half-row for all these specimens. The meristic
Table 2
Meristic variation in the radula of Chromodoris annulata.
Rows Maximum teeth/half-row
58 49
65 59
66 49
70 45
75 42
variations fall within the acceptable range of intraspecific
variation seen in dorid nudibranchs (BERTSCH, 1976a).
This is a significant addition to the tropical west Amer-
ican faunal province. Further research is needed to deter-
mine whether this species is actually a more common
member of the faunal province than the single collecting
record would indicate. It would then show a wider dis-
tribution pattern, similar to other opisthobranch species
reported to occur in this region originally based on just
one specimen, such as Dolabrifera dolabrifera (Rang, 1828)
(reported by BERTSCH, 1970), Berghia major (Eliot, 1903)
(reported by FARMER, 1966), and Spurilla alba (Risbec,
1928) (reported by SPHON, 1971).
Chromodoris galexorum Bertsch, 1978 (a)
This brightly colored nudibranch, with yellow borders
encircling its large red spots, is known from the central
and southern Gulf of California: from Bahia de los An-
geles (GOTSHALL, 1982:94) to La Paz, Baja California
Sur, and from Guaymas, Sonora, and nearby islands
(BERTSCH, 1978a).
The following record documents its more northerly oc-
currence outside the Gulf of California at an offshore
island along the Pacific coast of Baja California. It may
well represent an extra-limital thermally anomalous
“range extension” (ZINSMEISTER, 1974). The long period
of elevated water temperatures caused by an El Nino phe-
nomenon in the eastern Pacific (personal observations;
HALPERN et al., 1983) may explain the presence of this
tropical species at the periphery of the warm temperate
California faunal province.
(1) 1 specimen, subtidal, 13.7 m, Old Sealing Station,
on lee side of Isla Guadalupe, Baja California; leg. Jim
Gatewood and Patricia S. Mariano, 22 August 1983.
Chromodoris sphoni (Marcus, 1971)
The known distribution of the red-cross colored nudi-
branch, Chromodoris sphoni, is along the mainland Pacific
coast of Mexico and Central America, from Mazatlan,
Sinaloa, Mexico, to Panama Bay, Panama (BERTSCH,
1978a:321). The following specimens represent its first
report from inside the Gulf of California, and a north-
ward range extension of over 670 km:
(1) 1 specimen (17 mm long), subtidal, 18 m, Isla Santa
Catalina, Sonora (near Guaymas); leg. AK, June 1978.
(2) Approximately 30 specimens, subtidal, 12-18 m
Page 266 The Veliger, Vol. 26, No. 4
Explanations for Figures 1 to 6
Figures 1 and 2. Trapania sp. collected at Cabo San Lucas. Figures 4 to 6. Scanning electron micrographs of the radula of
Photographs by AK. Chromodoris annulata. Fig. 4, 111 x; Fig. 5, 89 x; Fig. 6, 222 x.
Figure 3. Chromodoris annulata collected at Isla Tortuga. Pho- SIBMIS ly LBUS.
tograph by AK.
H. Bertsch & A. Kerstitch, 1984
Page 267
deep, along the Sonora coast from Morro Colorado to
Bahia San Carlos; observed by AK, April—July, 1980-
1982.
Mexichromis antonu (Bertsch, 1976) (b)
This relatively rare chromodorid is known from various
scattered locations in the tropical west American faunal
province: 3 sites on the Baja California coastline (or near-
by islands) of the western Gulf of California; from the
Pacific southwest coast of Mexico (Santiago Bay, near
Manzanillo, Colima) and from the Pacific coast of Costa
Rica (BERTSCH, 1978b:80-82). These additional records
are the first reports of the species from the state of Sonora,
Mexico, and from the eastern side of the Gulf of Califor-
nia:
(1) 2 specimens (10 and 15 mm long), subtidal, 18 m,
Isla Santa Catalina, Sonora; /eg. AK, June 1978.
(2) 30-40 specimens, subtidal, 12-18 m, along the So-
nora coastline between Morro Colorado and Bahia San
Carlos; seen by AK, April-July, 1980-1982.
POROSTOMATA
DENDRODORIDIDAE
Doriopsilla rowena Marcus & Marcus, 1967
This small porostome has been collected in the northern
Gulf of California from the states of Sonora and Baja
California: Puerto Penasco (Marcus & Marcus, 1967:
205), Guaymas, San Felipe (KEEN, 1971:830), and Bahia
de los Angeles (POORMAN & PooRMAN, 1978:373). This
represents the first report of Doriopsilla rowena from the
state of Sinaloa and from the southern extreme of the Gulf
of California; moreover it is a southern range extension
of about 680 km.
(1) 1 specimen (8 mm long), Mazatlan, Sinaloa; Jeg.
Antonio J. Ferreira, March 1971.
DENDRONOTOIDA
BORNELLIDAE
Bornella sarape Bertsch, 1980
This dendronotid is known to occur on both sides of the
southern part of the Gulf of California, at Bahia Cari-
salito (4 km north of Bahia Las Cruces), Baja California
Sur, and at Sayulita, Nayarit (BERTSCH, 1980). The fol-
lowing data extend its known range 400 km north into
the central Gulf of California, and 200 km southward
along the west coast of Mexico:
(1) 6 specimens, intertidal, Bahia San Carlos, Sonora;
leg. Roy and Forrest Poorman, December 1976.
(2) 1 specimen, intertidal, Melaque, north end of Bahia
de Navidad, Jalisco; Jeg. F. Poorman, February 1976.
Bornella sarape is now known to occur along more than
1200 kilometers of the western coast of mainland Mexico,
with one collecting locality near the southern tip of the
Baja California peninsula.
TRITONIIDAE
Tritonia diomedea Bergh, 1894
The range of Tritonia diomedea along the Pacific coast
of the Americas is extensive; it is often cited as occurring
from the Aleutian Islands, Alaska, to the Bay of Panama,
Panama (BEHRENS, 1980:80). However, its known distri-
bution is disjunct, and should be more properly cited as
occurring from Shumagin Bay, Aleutian Islands, Alaska
(the type locality) to Punta Santo Domingo, on the outer
coast of Baja California just north of Bahia Magdalena
(KEEN, 1971:834). Between these locations many speci-
mens have been reported (see Marcus, 1961:32-33;
MaAcFARLAND, 1966:226-243; and THOMPSON, 1971, for
a summary of these data). It is also known from the Bay
of Panama and from Japan (Marcus, 1961; KEEN, 1971).
Hence, the only published record of Tritonia diomedea in
the tropical west American marine faunal province is from
its far southern waters, in Panama. There is presently a
gap in its known distribution between the outer coast of
Baja California (where it is known from the Surian prov-
ince) and Panama. The following collecting data represent
the first report of this species from the Gulf of California
and in the northern portion of the Panamic marine faunal
province:
(1) 1 specimen, dredged from 100 m, 3 km south of
Tetas de Cabra, Bahia San Carlos, Sonora; leg. Roy &
Forrest Poorman, 1 November 1980.
(2) 1 specimen, Morro Colorado, Sonora; leg. AK, 27
December 1979.
Many specimens of this species (especially those col-
lected in California and from Punta Santo Domingo and
Panama Bay) have been obtained by dredging. 7ritonia
diomedea may well be more common in the Panamic prov-
ince in deeper waters. The following data from shrimp
trawls indicate a temporal variation in the occurrence of
T. diomedea:
(3) Hundreds of specimens, dredged from 70 to 100 m
in shrimp trawls, between Bahia Kino and Bahia San
Carlos; observed by AK, December 1980 and 1981.
In the previous 12 years of sampling shrimp trawl ma-
terial from the fishermen in this area, 77itonia diomedea
did not appear until 1979. Not a single specimen had been
observed. Since 1981 this species seems to have again dis-
appeared from this area. During a recent trip (by AK,
December 1982) not a single specimen was observed among
20 separate trawl samples.
ARMINOIDA
ARMINIDAE
Histiomena convolvula (Lance, 1962)
This rare sand-burrowing arminid has been reported
from the Baja California coastline of the northern Gulf of
California: Punta Diggs, 24 km south of San Felipe
Page 268 The Veliger, Vol. 26, No. 4
Explanations for Figures 7 to 12
Figure 7. Scanning electron micrograph of the radula of Chro- Figures 10 to 12. Scanning electron micrographs of the radula
modoris annulata, 445 x. SEM by HB. of Histiomena convolvula. Fig. 10, 111 x; Fig. 11, 111 x; Fig.
Figures 8 and 9. In situ underwater photographs of Histiomena Is Grae) Pa SISIMIS |e) 7 Jes
convoluula eating the gorgonian Muricea. Photographs by HB.
H. Bertsch & A. Kerstitch, 1984
Page 269
15
Explanations for Figures 13 to 15
Scanning electron micrographs of the radula of Flabellina cynara. Fig. 13, 111 x; Fig. 14, 222 x; Fig. 15, 222 x.
(LANCE, 1962), and Bahia de los Angeles (POORMAN &
POORMAN, 1978:373). The following data further docu-
ment the presence of Histiomena convolvula in Bahia de
los Angeles and extend its range to the eastern Gulf of
California, along the Sonora coastline:
(1) 1 specimen, subtidal, 7.6 m, NE of Punta Gringa,
Bahia de los Angeles; /eg. HB and Tom Smith, 11 De-
cember 1981.
(2) 3 specimens, subtidal, 9 m, NE of Punta Gringa,
Bahia de los Angeles; Jeg. HB and David Myers, 25 Jan-
uary 1982.
(3) 1 specimen, subtidal, 29 m, Punta Doble, Bahia
San Carlos, Sonora; /eg. AK, 15 April 1979.
Three of the four specimens found by Bertsch, Smith,
and Myers in Bahia de los Angeles were eating the gor-
gonian Muricea cf. californica (Figures 8 and 9). This is
the first report of the prey of Histiomena convolvula. All
four specimens in Bahia de los Angeles were encountered
on the deeper seaward edge of a series of rock reefs, where
the bottom becomes sandy.
The radula consists of numerous hook-like teeth (Fig-
ures 10 and 11). LANCE (1962:53-54; fig. 6c) reported
that some of the middle lateral teeth bear extremely fine
denticles along the side of the cusp; these are clearly shown
in the scanning electron micrograph (Figure 12).
AEOLIDIIDA
FLABELLINIDAE
We follow GOSLINER & GRIFFITHS (1981) in the ge-
neric placement of these two species of Flabellina.
Flabellina cynara (Marcus & Marcus, 1967)
This elegant eolid is known to swim by back-and-forth
strokes of its whiplike cerata, bringing head and tail
rhythmically together. Flabellina cynara has been reported
Page 270
The Veliger, Vol. 26, No. 4
T T
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CHIHUAHUA
Figure 16
Map of northwestern Mexico showing collecting localities.
from various localities in the extreme northern Gulf of
California: Cholla Bay, Puerto Penasco, Sonora (MARCUS
& Marcus, 1967:220); dredged in 38 m of water off Con-
sag Rock (FARMER, 1970:84); and dredged off Puertecitos
(KEEN, 1971:836). The following records are southern
range extensions of over 430 km and 210 km respectively
along each side of the Gulf of California. The range of
Flabellina cynara can now be cited as throughout the
northern half of the Gulf of California.
(1) 1 specimen (45 mm long), subtidal, 12 m, Guaymas,
Sonora; leg. AK, 28 June 1981.
(2) 1 specimen, subtidal, 15 m, S end Smith Island,
Bahia de los Angeles, Baja California; /eg. David K. Mul-
liner, 17 October 1979.
The triseriate radula (Figures 13 to 15) had 18 rows
of teeth; it was a larger specimen than the holotype which
had 16 rows of teeth (Marcus & Marcus, 1967:221).
Each central tooth bears 7-10 denticles (rather than just
H. Bertsch & A. Kerstitch, 1984
the 7-9 originally reported). The scanning electron mi-
crographs (Figures 13 to 15) show a morphological vari-
ation that was not reported in the light-microscopy-based
original description. Some of the lateral teeth, “‘obtuse-
angled triangles” (Marcus & Marcus, 1967:221), bear
2 rows of denticles—the large and obvious grasping den-
ticles below the cusp on the inner surface and a row of 5
or 6 minute denticles on the outer slope of the tooth (Fig-
ures 13 and 14). As can be seen, not all teeth show this
feature.
Flabellina iodinea (Cooper, 1863)
The range of Flabellina iodinea has been cited as Van-
couver Island, British Columbia, Canada, to the Gulf of
California, Mexico (BRUSCA, 1980:194), to Puerto Pe-
nasco (BEEMAN & WILLIAMS, 1980:336-337), or to Bahia
de los Angeles (FARMER, 1980:122). However, known dis-
tribution records do not exist from the southern coasts of
Baja California, nor in the southern Gulf of California.
Previous collecting data should have been summarized to
reflect this disjunct known distribution: from Vancouver
Island to Cabo San Quintin (SPHON, 1972:64; BEHRENS,
1980:92; MCDONALD & NYBAKKEN, 1981:60), including
the Coronados Islands (LANCE, 1961) and Ensenada
(FARMER & COLLIER, 1963) in northern Baja California.
This species has been reported in the Gulf of California
from two locations: Puerto Penasco (MARCUS & MARCUS,
1967:218) and Bahia de los Angeles (POORMAN & Poor-
MAN, 1978:373; HAMANN, 1981).
The following data, therefore, are especially significant
because they establish its presence at intermediate locali-
ties along the Pacific coast of Baja California, at the ex-
treme southern tip of the peninsula, and from a second
locality in the eastern Gulf of California:
(1) BEHRENS (1983) reported collecting specimens at
Islas San Martin, San Benitos, and Cedros, Baja Califor-
nia.
(2) 3 specimens, intertidal, El Tomatal, Baja Califor-
nia; HB, 14 June 1983.
(3) 1 specimen, subtidal, 76 m, Cabo San Lucas, Baja
California Sur; leg. AK, August 1972.
(4) Punta Doble, Bahia San Carlos, Sonora; leg. AK.
various: 1 specimen, 29 m, April 1983; 1 specimen, 16.8
m, December 1978; 3 specimens, 29 m, April 1979; more
than 30 specimens, subtidal, April 1982.
Flabellina iodinea occurs rarely in the Gulf of Califor-
nia, but usually under situations of colder water, espe-
cially in deeper subtidal waters (our records; also those of
POORMAN & POORMAN, 1978, who dredged F. zodinea from
Bahia de los Angeles; and HAMANN, 1981, who reported
collecting it below the thermocline at 15 m in Bahia de
los Angeles). The single specimen collected at Puerto Pe-
Nasco is an exception to this generalization. With current
knowledge, we can best describe the range of F. zodinea
as common throughout the Oregonian and Californian
marine faunal provinces, from Vancouver Island, British
Columbia, to Isla Cedros, Baja California; rarer in the
Page 271
northern Panamic province (throughout the Gulf of Cal-
ifornia) in deeper or colder waters.
GLAUCIDAE
Glaucus atlanticus Forster, 1777
This species is a pelagic, circumtropical member of the
wind-driven Portuguese man-of-war (Physalia) commu-
nity (BERTSCH & JOHNSON, 1981:100). The toxic stinging
capability of Glaucus, which stores the largest and most
potent nematocysts of Physalia, is well documented
(THOMPSON & BENNETT, 1969; BINGHAM & ALBERTSON,
1974).
In the eastern Pacific it has been collected off west-
central America, from latitude 24°N, south to latitude 8°S
(KEEN, 1971:840). These data are the first records from
well inside the Gulf of California:
(1) Numerous specimens (10-20 mm), off Bahia San
Carlos, among drifts of Physalia and Porpita; observed by
AK, summers 1978, 1979, and 1981.
(2) Several hundred specimens (10-20 mm), off Cabo
San Lucas, among drifting Physalia and Porpita; observed
by AK, summers 1978, 1979, and 1981.
AEOLIDIIDAE
Baeolidia nodosa (Haefelfinger & Stamm, 1958)
This species is widely distributed in the tropical east
and west Atlantic, including the Mediterranean and Ca-
ribbean Seas (HAEFELFINGER & STAMM, 1958; Marcus
& Marcus, 1970:89; SCHMEKEL, 1972:152-159; TEm-
PLADO, 1981). In the central Pacific Ocean it has been
reported from Oahu and Kauai, Hawaiian Islands (Kay,
1979:488; GOSLINER, 1980:66-69; BERTSCH & JOHNSON,
1981:102), and in the eastern Pacific in the Gulf of Cal-
ifornia from Bahia Las Cruces, Baja California Sur
(BERTSCH, 1972:104-105).
The following record is only the second report of this
species in the Gulf of California, and a northward range
extension (of over 400 km) from Bahia Las Cruces to the
Sonoran coast:
(1) 1 specimen, on floating Sargassum, off Bahia San
Carlos, Sonora; leg. AK, June 1978.
Spurilla neapolitana (Delle Chiaje, 1823)
This eolid has been reported numerous times through-
out the tropical Atlantic, including the Mediterranean and
Caribbean Seas (cf. GOSLINER, 1980:64-65, for a sum-
mary of the literature and synonymy). Moreover, this
species has been reported from the central Pacific (Oahu,
Hawaiian Islands; Kay, 1979:489; GOsLINER, 1980) and
the eastern Pacific (“Gulf of California”; BERTscH, 1979:
59). It thus shares a similar distribution pattern with
Baeolidia nodosa: throughout the tropical Atlantic (and ad-
jacent seas); Hawaii, and Gulf of California in the central
and eastern Pacific. This species’ distribution is not ap-
propriately termed “‘circumtropical” (Kay, 1979;
Page 272
The Veliger, Vol. 26, No. 4
GOSLINER, 1980) since it has not yet been reported from
the Indo-West Pacific.
The following data detail known collecting sites in the
Gulf of California:
(1) 1 specimen (55 mm long), intertidal, Morro Colo-
rado, Sonora; leg. AK, 19 December 1977 (deposited egg
mass in aquarium).
(2) 1 specimen, subtidal, 9 m, off Isla San Nicholas,
Bahia San Carlos, Sonora; leg. AK, December 1979 (laid
eggs in aquarium).
(3) 3 specimens (25 mm long), intertidal, Puerto Es-
condido (24 km south of Loreto), Baja California Sur; leg.
Robin Hugh Alexander Boroch and Deborah J. Kasten,
28 June 1980.
ACKNOWLEDGMENTS
We thank our scuba diving partners for assisting us in
our field work in the Gulf of California: Tom Smith,
David Myers, and Myra Muramoto.
We are grateful to Ramon Moreno Castillo and Gil-
berto Fuentes G., scientific illustrators for the Instituto de
Investigaciones Oceanologicas, and David K. Mulliner, of
San Diego, for their artistic and photographic assistance.
We thank Luis Aguilar Rosas, research scientist of the
I.1.0., for his support.
We were privileged to be able to include the data of
Antonio J. Ferreira, David K. Mulliner, Roy and Forrest
Poorman, Robin Hugh A. Boroch and Deborah J. Kas-
ten, and Jim Gatewood.
We thank David W. Behrens, Sandra Millen, and
Terrence M. Gosliner for assistance with the manuscript.
The senior author is grateful to Anthony D’Attilio, Hugh
Bertsch, Nancy Love, and Fay Wolfson.
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The Veliger 26(4):274-281 (April 2, 1984)
THE VELIGER
© CMS, Inc., 1984
The Diets of Alaskan Neptunea
by
RONALD L. SHIMEK'!
University of Alaska, Anchorage, and
University of Washington, Friday Harbor Laboratories
Abstract.
Diets of Neptunea pribiloffensis, N. lyrata, N. heros, and N. ventricosa from a series of
subtidal sites in the Bering Sea, and N. lyrata and N. pribiloffensis from an intertidal habitat in south-
central Alaska, were examined and compared. All species were found to feed primarily upon bivalves
and polychaetes, secondarily upon carrion. Neptunea pribiloffensis, in particular, appears to feed on live
polychaetes and bivalves. Other prey taxa are well represented in the diets of these large whelks.
In the Bering Sea, these four species are found in two paired groups. Neptunea heros and N. ventricosa
are the more northern, colder-water pair, and N. pribiloffensis and N. lyrata are the southern, warmer-
water pair. Diets of each species within each pair are similar and the pooled diets of both species within
each pair are similar when both pairs are allopatric. When all four species are sympatric, the diets
overlap significantly less. Similarly, the diets of N. lyrata and N. pribiloffensis from south-central Alaska
overlap substantially with the diets of all four species from the non-overlap regions of the Bering Sea,
but overlap significantly less with diets of all four species from the region of sympatry.
INTRODUCTION
LARGE GASTROPODS OF the family Buccinidae, often very
abundant in north-temperate and boreal areas (PETERSEN,
1911a, b, 1913; BLEGVAD, 1914; NIELSEN, 1975; NaGalI
& SupDA, 1976; PEREYRA et al., 1976; TayLor, 1978;
TAYLOR et al., 1980), are presumed to be carrion feeders
and facultative carnivores. Considering the diversity of the
family (BAXTER, 1981) and the relatively large size and
economic importance of the snails, however, their diets
are relatively unknown (BLEGVAD, 1914; HUNT, 1925;
AVERY, 1961; PEARCE & THORSON, 1967; VILLEMURE &
LAMOUREUX, 1975; TAyLor, 1978).
In the eastern Bering Sea and in south-central Alaska,
the dominant marine gastropods, in size and biomass, be-
long to the buccinid genus Neptunea. Neptunea is circum-
boreal, but has a center of distribution in the north-central
Pacific-Bering Sea region (NELSON, 1978). The diet of
the European Neptunea antiqua (Linnaeus, 1758) has been
examined (PEARCE & THORSON, 1967; TAYLOR, 1978),
but few feeding observations have been made for any of
the Pacific species (AVERY, 1961). The four largest and
most abundant species of Neptunea in the eastern Bering
Sea are N. lyrata (Gmelin, 1791), N. pribiloffensis (Dall,
1919), N. heros (Gray, 1850), and N. ventricosa (Gmelin,
1791). Together with some other large gastropods, they
‘ Mailing address: Bamfield Marine Station, Bamfield, British
Columbia VOR 1B0O, Canada.
are the basis for a small pot fishery in the Bering Sea
(MacINTOsSH, 1978). In most Atlantic areas, however,
buccinids have been considered an economic nuisance
(PETERSEN, 1911b), although recently some attempts have
been made to assess population sizes in anticipation of
fisheries attempts (VILLEMURE & LAMOUREUX, 1975).
Information on the Bering Sea neptunes is fragmentary
(PEREYRA et al., 1976; MACINTOSH & PAUL, 1977); none-
theless, they are clearly an important component of that
region’s benthic fauna. The Bering Sea benthos consists
of two major faunal assemblages, each somewhat corre-
lated with depth, and certainly correlated with character-
istic bottom-water temperatures. The low-Arctic—Boreal
assemblage, found in the northwestern portions of the
Bering Sea, is correlated with bottom temperatures ex-
ceeding 2°C only briefly in the summer, generally is found
in depths in excess of 50 m, and contains N. heros and N.
ventricosa. The Subarctic—Boreal assemblage, found in the
southern and southeastern portions of the basin, exists
where the bottom temperature is a relatively constant 2-
4°C, is characteristic of shallow waters, and contains N.
lyrata and N. pribiloffensis (NEIMAN, 1963; NAGAI & SUDA,
1976; PEREYRA et al., 1976; MACINTOSH & PAUL, 1977).
The replacement of one faunal assemblage by the other
occurs in a transition zone often in excess of 50 km wide.
With the exception of several cosmopolitan species, main-
ly polychaetes, most invertebrate benthic taxa are repre-
sented by different species in the two regions (NEIMAN,
1963).
R. L. Shimek, 1984
Portions of the Subarctic-Boreal assemblage are found
south of the Aleutians. In particular, N. lyrata and N.
pribiloffensis have ranges extending to at least the Wash-
ington coast. They appear to follow a thermal gradient,
for they are characteristically deep-water species there
(RIcE, 1972; ABBoTT, 1974). Both species are found in-
tertidally in south-central Alaska. In some cases, they are
the most abundant gastropods in the low intertidal zone
(SHIMEK, 1981).
Buccinid gastropods are presumed to be primarily scav-
engers or carrion feeders. This assumption is based on
three premises. Firstly, they lack the accessory boring or-
gan found in the muricid gastropods; consequently, they
are unable to attack efficiently bivalve or barnacle prey
by boring. Secondly, they come readily to bait. And final-
ly, those few whose diets have been examined have been
shown to eat a wide variety of prey. Based on preliminary
field observations, I hypothesized that Alaskan Neptunea
are predatory and only rarely eat carrion. I asked the
following questions. What is the diet of each species? Is
there any specialization with regard to either prey taxon
or prey guild? Can the food be characterized as having
been alive or dead? What is the overlap in the diets of
sympatric species? If they are predominantly scavengers,
the dietary overlaps should be higher than if they are
predators, assuming some predator-prey specialization.
And, in areas of geographical overlap, are the diets of the
species similar?
I examined gut contents of adults and large juveniles of
the four Neptunea species. By identifying the snails’ gut
contents as precisely as possible, I hoped to determine
their diets. Neptunea is a large genus containing many
similar species (GOLIKOV, 1961, 1963; NELSON, 1978),
and the radulae are similar and unspecialized in the species
examined (KANG, 1976; Shimek, unpublished observa-
tions). Feeding structures are often strongly correlated with
the prey taken, especially in specialized carnivorous gas-
tropods (NYBAKKEN, 1970; NyBAKKEN & McDONALD,
1981; SHIMEK, 1983a), although the adaptive significance
of some of these structures remains obscure. The similar-
ities in the radulae and the similar gut morphologies of
all four Neptunea species examined indicate prey items
are probably captured and digested similarly in these
species.
MATERIALS anp METHODS
Bering Sea snails were collected using an Eastern otter
trawl constructed with 10.2-cm mesh on the wings and
body and 8.5-cm mesh in the intermediate section and
cod-end. The cod-end was lined with 3.2-cm mesh. Few
snails smaller than 50 mm in total length were collected.
Furthermore, as the net’s behavior on the bottom was
unpredictable, the samples from different sites must be
considered qualitative; however, they were assumed to be
comparable. Trawl-collected animals were either pre-
served in 70% isopropyl alcohol or frozen. Trawl-collected
Page 275
ALASKA
*
2
Figure 1
Map of Alaska showing snail collecting sites. A, region of N.
lyrata and N. pribiloffensis pair only; B, region where all species
are found; C, region of N. heros and N. ventricosa pair only; H,
intertidal site near Homer, Alaska. Numbers refer to the col-
lecting sites detailed in Table 1.
specimens came from several locations in the Bering Sea
(Table 1, Figure 1).
Field observations were made on a mixed N. lyrata-N.
pribiloffensis assemblage living on a low (—1.0 to —1.5m
below MLLW) intertidal sandstone bench near Homer,
Alaska (59°38'N; 151°27'W), to determine feeding meth-
Table 1
Bering Sea snail collection localities.
Number
collected
Nae Neptunea
Area Position ber lyr. prib. vent. heros
A 54°59'N; 165°09’'W 1 18
A 55°59'N; 165°10’W 2 116 3638
A 56°39'N; 165°09'W 6 2 1
A 56°20'N; 164°35'W 5 48
B 56°19'N; 165°12'W 4 i Dil
B 56°39'N; 164°13’W 7 45 7 68 14
B 57°39'N; 169°39'W 8 32
Cc 56°20'N; 165°47'W 3 63
C 58°00'N; 164°01’W 9 54 100
Page 276
The Veliger, Vol. 26, No. 4
Table 2
Gut contents of Neptunea species. * =
Species: N. pribiloffensis
Area: A B H A
Contents:
Hydrozoa
Polychaeta 7 14 29 14
Cirripedia 4
Decapoda 1
Bivalvia 9 28 26
Gastropoda
Ophiuroidea
Osteichthyes 1
Sand 14 9 23 25
Unidentified 3 26 6
TOTAL FEEDING 34 23 106 76
(98)*
No contents 53 18 72 60
TOTAL 87 41 170 136
ods, and to assess the range of prey taken. Field-collected
animals were frozen for later analysis. Band transects were
done monthly from May through September, 1979, to
assess the number of animals in each habitat.
Feeding animals were noted and their food was deter-
mined if possible. The intertidal bench was a heteroge-
neous area consisting of three major habitats: a silt-cov-
Some Homer N. pribiloffensis had more than one item in their guts.
N. lyrata N. heros N. ventricosa
B H B C B C TOTAL
3 3 6
2 3 12 1 13 95
2 1 4 6 17
1 2
1 7 7 8 3 21 110
2 2
1 1
1 il 3
3 12 5 11 3 16 121
6 5 5 16 20 9 96
13 27 22 51 35) 66 453
(445)*
32 25 24 49 53 51 437
45 52 46 100 88 117 882
ered sandstone bench area, areas of cobble, and areas of
dense mats of the sabellid polychaete Schizobranchia insig-
nis Bush, 1904. Samples of the infauna were collected by
recovering all of the sediment from 0.25-m? randomly
placed quadrats in the worm-mat areas and the silt-cov-
ered inter-mat areas. Sediment collected for analysis was
fixed for 24 h in 10% seawater-formalin, stained with
Table 3
Dietary overlaps of Neptunea species by area.
# Species—Area 1. 2s 3}
1. N. lyrata—A O O
2. N. pribiloffensis—A 0.841 oO
3. N. pribiloffensis—H 0.802 0.868
4. N. ventricosa—C 0.934 0.829 0.808
5. N. lyrata—H 0.922 0.829 0.791
6. N. heros—C 0.686 0.745 0.833
7. N. lyrata—B 0.561 0.721 0.750
8. N. heros—B 0.667 0.529 0.491
9. N. ventricosa—B 0.400 0.333 0.333
10. N. pribiloffensis—B 0.500 0.412 0.509
OOO]
0.812
0.692
0.567
0.659
0.504
0.317
3) 6. Te 8. 9. 10.
O @ @ @ @ @
O t @ @ Oo @
@ O @ @ Oo ®
oO @ t @ @ Oo
@ @ @ O O
0.633 ® O @ @
0.550 0.750 O O ©
0.583 0.333 0.250 @ a
0.333 0.438 0.333 0.417 a
0.300 0.500 0.500 0.000 0.083
Mean + 1 SD < D < Mean + 2 SD = 0.795-1.000 indicated by: O
Mean D = 0.570 + 0.224
Mean — 1 SD S D S Mean + 1 SD = 0.346-0.794 indicated by: @
Mean — 2 SD < D < Mean — 1 SD = 0.121-0.345 indicated by: 0
D < Mean — 2 SD = 0.000-0.120 indicated by:
H,:D,; > D, where i= A, B, C, H; and where j, k = A, C,
Mean D,, = 0.454 + 0.177 N = 30
Mean D,, = 0.802 + 0.084 N=15
H.
Calculated t = 7.18, 43 d.f.
to.001 ,60
= 3.460; therefore reject H, with a < 0.001
R. L. Shimek, 1984
oe
MA M J J A _ §S
Figure 2
Relationship between percent of animals observed feeding (mean
+ 1 SD) and the number of hours between sunset and dawn.
Left ordinate gives percent feeding (@), where numbers indicate
the number of snails examined during a given sampling period.
Right ordinate gives hours between sunset and sunrise at this
latitude (indicated by the solid line). Spearman Rank Correla-
tion Coefficient between observed feeding percentage and sunset-
sunrise time = 1.
Rose Bengal, and stored in 70% isopropyl alcohol. The
sediment was sieved through 0.5-mm screens and animals
retained on the screens were identified. Polychaetes and
bivalves, potential prey, were identified to species; other
taxa were generally identified to class.
Snails returned to the laboratory were removed from
the shell, sexed, and the stomach and hindgut were ex-
amined for contents. Preliminary examination of the mouth
and esophagus in 150 animals yielded no contents; thus,
examination of the foregut was not done for the majority
of the specimens. Gut contents were examined microscop-
ically and identified if possible, using standard references.
Results were analyzed using t-tests, and log-likelihood
ratios (SOKAL & ROHLF, 1969). Similarity in diets was
compared using the common lowest percentage or “D”
index (SCHOENER, 1968).
RESULTS
Gut contents of 128 N. lyrata, 181 N. pribiloffensis, 146
N. heros, and 205 N. ventricosa from the eastern Bering
Sea were analyzed by area. Similarly, the gut contents of
52 N. lyrata and 170 N. pribiloffensis from the Homer
area were examined (Table 2).
About half of the animals examined had empty guts.
The others contained a wide variety of items, but gener-
ally the most abundant recognizable items were bivalve
fragments (ctenidial remains, shell fragments, or cuticular
siphonal coverings), polychaete remains (fragments with
Page 277
0.60 ;-
N 0.50
u Joo N. pribiloffensis
M e
B CHEM! ha
E
R 0.30
we
0.20 N. lyrata
Le
+
1979
Figure 3
Observed abundance of Neptunea spp. at site H.
setae or whole worms), or barnacles (trabeculate plates,
cirri, or entire animals except for the calcareous plates).
A large fraction of the contents consisted of sand and
unidentifiable tissue fragments. These categories were ex-
cluded from the dietary overlap analyses. The absolute
and relative frequencies of these categories varied from
species to species, and within species from area to area.
Dietary overlap analyses were done using only the
identifiable gut contents. To ensure consistency of inter-
pretation, the general systematic category utilized was class
(Table 2). Bering Sea snails exhibited substantial differ-
ences in diet within a species between areas of non-overlap
(Areas A, C) and overlap (Area B, Table 3). Neptunea
lyrata and N. pribiloffensis diets within area A overlap
substantially, as do the diets of N. heros and N. ventricosa
within area C. Furthermore, these two pairs of species
have diets that overlap to a high degree (Table 3). The
diets from area B are much less similar. There is a general
trend for any species’ diet in the overlap area to be dif-
ferent from its diet in either area A or C. There is also
high overlap between the diets of N. lyrata and N. pribi-
loffensis from the Homer area, and these diets are similar
to the diets of the respective species from area A. The
mean dietary overlap for all species combinations between
and within areas A, C, and H is significantly higher than
the mean dietary overlap for all species combinations be-
tween areas A and B, C and B, H and B, and all species
combinations within area B (Table 3).
Field observations of feeding at Homer generally con-
firm the diet as consisting of either polychaetes or bivalves,
although the fraction of snails feeding is very low com-
pared to the fraction with food in their guts (Table 4).
The number and fraction of N. pribiloffensis observed
feeding varied monthly, and were highly correlated with
the amount of time between sunset and sunrise, indicating
that feeding is largely nocturnal, at least intertidally (Fig-
ure 2).
Page 278
Frequency of dietary items.
Species:
Area:
Contents:
Hydrozoa
Polychaeta
Cirripedia
Decapoda
Bivalvia
Gastropoda
Ophiuroidea
Osteichthyes
Sand
Unidentified
Nothing
TOTAL
Number
N. pribiloffensis
B H
0.34 0.18
0.16
0.22 0.14
0.15
0.44 0.42
1.00 1.05*
41 170
The Veliger, Vol. 26, No. 4
Table 4
* = More than one food item per snail for some categories.
Field feeding
Gut contents observations
N. lyrata N. heros N. ventricosa pribi-
B H B Cc B Cc loffensis WN. lyrata
0.03 0.03
0.18 0.06 0.12 0.01 0.11 0.02 0.01
0.04 0.03 0.05
0.02 <0.01
0.02 0.13 0.15 0.08 0.03 0.17 0.02 0.03
0.04
0.02
0.01 0.01
0.07 0.23 0.11 0.11 0.03 0.14
0.13 0.10 0.11 0.16 0.23 0.08
0.71 0.48 0.52 0.49 0.60 0.44 0.95 0.97
0.99 1.00 0.99 0.99 0.97 1.00 0.99 1.01
45 52 46 100 88 17 1125 185
Estimates of prey availability are not present for the
Bering Sea populations, but are available for the intertidal
population (Table 5). The sabellid Schizobranchia insignis,
the relatively large rock-burrowing bivalve Zirfaea pilsbryi
Lowe, 1931, and polychaetes in general are abundant.
Taxon
Cnidaria
Phoronida
Priapulida
Annelida
Oligochaeta
Polychaeta
Maldanidae
Nephtyidae
Nereidae
Pectinariidae
Polynoidae
Sabellidae
Others
Mollusca
Bivalvia
Zirfaea pilsbryr
Others
Gastropoda
Arthropoda
Echinodermata
TOTAL
Worm
18,800
6756
40
46
230
41,598
7677
22
3893
186
3406
86,654
It Hot He
I+
Carrion suitable for scavengers was seen occasionally, but
was too rare for quantitative abundance estimates to be
meaningful. Both species of Neptunea were relatively
abundant in this intertidal area (Figure 3).
Only within the Polychaeta was prey discrimination to
Table 5
Infaunal organisms at Homer area.
mat
May
Mean number per m? + 1 SD
September
Bare bench Worm mat Bare bench
525 + 742 3175 + 601
20 + 6 8+ 11
G} ae Jil
2019 + 547 20,000 + 20,365 1050 + 212
IG se 2B 5350 + 1061 125 + 106
Sil ae il 400 + 424
600 + 34 650 + 261 220 + 28
900 + 849
367 + 58 200 + 282
15,385 + 5071 16,250 + 1060 50 + 72
15,385 + 4606 23,050 + 1095 83,320 + 45,368
Wg) se Bij WD, de BS) 20 + 24
600 + 237 10,300 + 1229 1678 + 2011
238 + 274
13,270 + 4624 15,300 + 6075 11,050 + 1485
50 +71
48,448 + 6856 94,472 + 16,663 100,621 + 20,743
R. L. Shimek, 1984
Page 279
Table 6
Polychaete prey of Neptunea.
Species: N. pribiloffensis
Area: H A B H
Family:
Spionidae 2
Cirratulidae 2
Maldanidae 1 1 9 1
Polynoidae 1
Nereidae
Nephtyidae
Sabellariidae
Pectinariidae
Ampharetidae
Terebellidae 3
Sabellidae 20 1
Unidentified 0) 2, 2 0)
TOTAL
Pn Wd
—
a systematic category lower than class possible. Polychaete
remains were generally identifiable to family and occa-
sionally to species, although the lack of specimens for con-
firmational comparison of setal morphologies from the
Bering Sea areas makes the latter identifications some-
what doubtful. Some similarity is seen in the polychaete
prey taken when considered area by area (Table 6). Er-
rant polychaetes, absent from the guts of the Bering Sea
snails, were commonly found in the guts from the Homer
N. pribiloffensis. Maldanids seemed to be a favored food
for N. lyrata and N. pribiloffensis, whereas cirratulids were
taken more frequently by N. heros and N. ventricosa.
DISCUSSION
The large Neptunea species of the eastern Bering Sea and
south-central Alaska are clearly divisible into two groups
of species pairs of similar dietary and habitat utilizations.
When the two groups are allopatric, the northern, colder-
water pair, N. heros and N. ventricosa, has a high dietary
overlap with the southern group, N. lyrata and N. pribi-
loffensis. The benthic fauna in the Bering Sea is charac-
terized by a few widely spread assemblages and a larger
number of smaller, more local ones (NEIMAN, 1963). Re-
placement of one major assemblage by another is gradual,
and is often accomplished by the replacement of one species
by another similar species (7.e., N. heros by N. lyrata; N.
ventricosa by N. pribiloffensis) rather than by wholesale
changes in the character of the fauna (NEIMAN, 1963).
Quantitative data for changes in the infauna in this region
are not available, but given the noted gradual changes in
the epifauna (PEREYRA et al., 1976) and similar qualita-
tive observations about the infauna (NEIMAN, 1963), it is
reasonable to infer that the composition of the infauna at
the class level is relatively consistent.
The dietary similarity between the Homer and Bering
N. lyrata
aDnNre
N. heros N. ventricosa
B B C B C TOTAL
1 3
8 6 19
1 15
1
2
3
2
1
2 2
1 1 6
3) 27
2 0 12 1 13 39
2 0) 23 1 25 120
Sea populations of the N. lyrata-N. pribiloffensis group
strengthens the argument that this pair of species chooses
similar prey categories wherever it is found. The two hab-
itats are strikingly different; the Homer area is a rocky
sandstone beach, whereas the Bering Sea area A is a rel-
atively flat sandy subtidal plain, yet the diets show a high
degree of overlap at the class level.
If scavenging is defined as eating carrion, then tubico-
lous polychaetes and bivalves are unlikely items to be rep-
resented in the diets of scavengers. Both prey types bury
in the substrate and upon death are immediately covered
by sediment. Neptunea could be scavenging food, however,
from the remains of some other organisms’ meals. The
presence of entire polychaetes and barnacles, and, effec-
tively, the remains of entire gastropods (no shell; the re-
mains were macerated, but substantially complete) argue
against this. Furthermore, field feeding observations in-
dicated N. pribiloffensis and N. lyrata can easily eat large
bivalves that cannot close their shells completely.
The piddock Zirfaea pilsbry: is commonly found bur-
rowed into the sandstone of the Homer area. Both Nep-
tunea species feed on it by extending their proboscides
down the siphon and rasping away the flesh of the body.
A specimen of Neptunea pribiloffensis with a shell length
of 40 mm can extend its proboscis over 35 cm, allowing
easy feeding on buried infauna. In the Bering Sea sam-
ples, many of the bivalve remains contained rolled masses
of cuticle, which when unrolled were obviously the cu-
ticular coverings from clam siphons similar to the siphons
of Mya. Mya species gape; and Mya truncata, a common
arctic bivalve, is present in the Bering Sea (NEIMAN, 1963;
ABBOTT, 1974).
In the Homer area, many individuals of N. pribiloffensis
were seen feeding similarly on the sabellid polychaete
Schizobranchia insignis. They would extend their probos-
cides into the polychaete tubes and eat the worms. The
Page 280
worms are gregarious and their tubes often tightly inter-
twine. It is likely that worms adjacent to the one whose
tube was initially penetrated also are eaten. As many as
five specimens of S. insignis were found in the gut of one
N. pribiloffensis. Other polychaetes were taken by N. pri-
biloffensis, and these prey do not appear to be randomly
selected, as some taxa eaten are rare in the sediment sam-
ples. The significance of these choices remains unclear.
Neptunea pribiloffensis is clearly adept at capturing errant
as well as tubicolous sedentariate worms, indicating that
this species in particular can be a predator on mobile prey.
The analysis of the polychaete prey also shows that the
similarities seen in diets are to some extent an artifact of
the analysis. Within the class Polychaeta, the prey taken
are distributed among 11 families and probably more than
20 species. Thus, although these whelks form a predatory
guild adapted to exploiting polychaetes and bivalves, it is
unlikely that they are in direct competition with one
another for any one species of prey.
Bivalves have been shown to be important dietary com-
ponents in these (present study) and other Neptunea
(BLEGVAD, 1914; PEARCE & THORSON, 1967; TAYLOR,
1978), and I suspect both the sand and unidentified tissue
remains to be primarily the result of consuming bivalves.
Bivalve tissues have few overt structural clues as to taxo-
nomic origin and, thus, are difficult to identify when par-
tially digested. The dense sand probably passes through
the guts of Neptunea slower than most tissue fragments,
resulting in some specimens containing only sand in their
guts. In many specimens, gut contents clearly identifiable
as being of bivalve origin contained a large fraction of
sand in the midgut and unidentifiable tissue fragments in
the hindgut. In most cases then, the categories of sand and
unidentifiable tissue fragments probably represent the re-
mains of deposit-feeding bivalves, or bivalves that inad-
vertently ingested sediment. Items clearly dead when eat-
en were a small constant dietary fraction for all four
species. These items included fish remains (scales and tis-
sue), king crab (Paralithodes sp.) remains (a dactyl), and
a complete pandalid shrimp molt. The ophiuroid remains
collected in one N. heros included only fragments of one
ray, and may indicate scavenging. In the intertidal area,
no N. lyrata and only one of 1125 N. pribiloffensis were
observed eating carrion, a small dead Cancer magister.
CONCLUSIONS
Neptuneid gastropods must be considered to be primarily
predators on live prey, not scavengers or carrion feeders.
This conclusion is supported by the predominance of live
food in the diet and the dietary shift seen in the overlap
zone. The distribution of carrion should be relatively in-
dependent if viewed at the class level, providing the faunal
assemblages are generally comparable. The array of uti-
lized prey is less diverse than the array of potential prey
in the Homer area, indicating specialization on the de-
scribed prey. The dietary shifts would be expected when
The Veliger, Vol. 26, No. 4
two food-limited systems overlapped, as each competing
species pair was forced to utilize a more diverse, but less
desirable suite of food, although it is unlikely that direct
competition exists for any one prey species.
These four species exist as two paired species guilds
adapted for exploitation of deeply dwelling or large in-
fauna, although they are not bound to the resource. The
extremely long proboscides of these snails are probably
the major structural adaptations allowing exploitation of
the large bivalves and tubicolous polychaetes as major re-
sources. The snails are morphologically very similar and
the diets within each guild are also quite similar. They
are, however, reproductively isolated; each species has dis-
tinctly different egg capsules (GOLIKOv, 1963; SHIMEK,
1981). Predation on boreal soft-sediment infauna is un-
common among large prosobranchs. The naticids appear
to be the only other successful group of large snails to
exploit this resource. Because of their ability to bore shells,
the naticids are apparently specialists on mollusks. The
neptuneids exploit a wider array of potential prey, in-
cluding polychaetes and cirripedes. In most soft-sediment
communities, polychaetes are a major constituent in terms
of species number, absolute number, and biomass. The
polychaetes harvested by these Neptunea are large, al-
though the juveniles probably take smaller worms.
Soft-sediment vermivory is best exemplified in proso-
branchs by the immensely large and successful family
Turridae (SHIMEK & KOHN, 1981; SHIMEK, 1983a, b, c),
but the turrids in the north-central and north-eastern Pa-
cific are generally small. These small snails, primarily in
the genus Oenopota, appear to be largely specialist ver-
mivores (SHIMEK, 1983c). Oenopota species are abundant
and common in Alaskan waters (BAXTER, 1981), and nep-
tuneids may have faced substantial competitive pressure,
which forced them away from specialization on poly-
chaetes. Moreover, the large size of the neptuneids may
require more energy input per unit time than a steady
diet of small polychaetes alone can provide.
ACKNOWLEDGMENTS
This work was partially supported by the U.S. Depart-
ment of Commerce, National Oceanographic and Atmo-
spheric Administration, National Marine Fisheries Ser-
vice (P.O. 01-8-D19-00079) and the University of Alaska,
Anchorage, through a summer research grant. I thank
Mary Beattie for field and laboratory assistance, and Rox-
ie Fredrickson for laboratory assistance. Lee Ann Gard-
ner provided many of the analyses herein, and was a
valuable co-worker and associate. The facilities of the
University of Washington Friday Harbor Laboratories
were used with the permission of the director, Dr. A. O.
D. Willows. Several of my students and associates at the
University of Alaska, Anchorage, provided field assistance
and IJ thank them all. I thank the captain, crew, and sci-
entific party of the R/V “Oregon” during cruise 78-1 for
assistance and support. Richard MacIntosh helpfully and
R. L. Shimek, 1984
freely shared his Bering Sea gastropod expertise and col-
lections. Earlier drafts of this paper have been reviewed
by A. J. Kohn, R. Scheltema, and anonymous reviewers
who have provided many helpful suggestions.
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The Veliger 26(4):282-287 (April 2, 1984)
THE VELIGER
© CMS, Inc., 1984
Spatial Distribution of Three Species of Bivalves on an
Intertidal Flat: the Interaction of Life-history
Strategy with Predation and Disturbance
MARK L. BOTTON
Excel Division, Fordham University, College at Lincoln Center, New York, New York 10023
Abstract. Spatial distributions of three species of bivalves, Gemma gemma, Mulinia lateralis, and
Mya arenaria, were examined on a Delaware Bay intertidal flat inhabited by large numbers of horseshoe
crabs, Limulus polyphemus. Populations within and outside of predator exclosures were compared.
Gemma gemma, which has no actively swimming larval stage, was strongly aggregated after settlement.
Larger individuals in protected plots remained aggregated, but in unprotected plots, there was some
tendency toward randomization. Mulinia lateralis, which has planktonic larvae and actively burrowing
juveniles, was most aggregated just after settlement. Protected individuals of M. lateralis were much
more numerous, and were less aggregated, than unprotected M. lateralis. Mya arenaria also has a
planktonic larval stage, but juveniles are somewhat less motile. Protected individuals were initially
aggregated and remained so; predators eliminated nearly all unprotected M. arenaria.
INTRODUCTION
KNOWLEDGE OF THE spatial distribution of organisms is
important to expedient sampling, and spatial patterns may
also provide information on inter- or intra-specific rela-
tionships. Clumping or aggregation must be considered in
designing a sampling strategy (GAGE & GEEKIE, 1973;
Moore & MCLAUGHLIN, 1978; BoTToN, 1979; DOWNING,
1979). Spatial patterns may reflect physical variability in
substratum, or be indicative of biological interactions. For
example, spatial pattern in spionid polychaetes and its
relationship to aggressive behavior was reported by LEVIN
(1981).
Life-history strategies may influence spatial distribu-
tions of bivalves (BRADLEY & COOKE, 1959; MATTHIES-
SEN, 1960; JACKSON, 1968; GREEN & Hosson, 1970;
THOMPSON, 1982). Juveniles of species that brood larvae,
such as Gemma gemma, may be aggregated (JACKSON,
1968; THOMPSON, 1982), as with a “‘seed shadow” about
a parent tree. The spatial pattern of species with plank-
tonic larvae is difficult to predict; hydrographic factors
such as water temperature and salinity may influence the
dispersion of larvae prior to metamorphosis, and condi-
tions of the settlement surface, including the presence of
predators, are also significant (THORSON, 1966; WoopIN,
1976). After settlement, waves and currents may redis-
tribute bivalves (MATTHIESSEN, 1960; JACKSON, 1968;
THOMPSON, 1982).
Predation may also influence the spatial distribution of
bivalves. In theory in a heterogeneous environment, pred-
ators should concentrate their feeding in the richest patches,
and remain until their net rate of energy intake in these
patches falls to the average value for the habitat (HUGHES,
1980; StH, 1982). Such “optimal patch use” predators
should therefore equalize prey density among patches.
A caging study that excludes predators is a straightfor-
ward approach to studying the effect of predation on spa-
tial distribution of bivalves within comparably sized caged
and uncaged plots. SCHNEIDER (1978) found that shore-
birds equalized the spatial dispersion of the prey on a
Massachusetts mudflat. The present paper describes a cage
study conducted on intertidal sand flats in Delaware Bay,
New Jersey, in the spring-summer of 1978 and 1979.
Population censuses of the horseshoe crab, Limulus poly-
phemus (Linnaeus) (BOTTON, 1984), and bird-exclosure
treatments (BOTTON, 1983) strongly suggested that the
principal predator and sediment disturber was L. poly-
phemus, which utilizes these beaches for several months
for reproduction. Effects of caging on the abundance and
size-frequency distributions of bivalves are considered in
another paper (BOTTON, 1984). Here, I consider the in-
fluences of life histories, predation, and disturbance on the
spatial patterns of the three most abundant species of in-
faunal bivalves, two with planktonic larvae—Mya are-
naria Linnaeus, 1758 (Myacidae) and Mulinia lateralis
M. L. Botton, 1984
Page 283
Table 1
Mean (x) and Coefficient of Dispersion (CD) for the three most abundant bivalve species in the 1978 predator exclosure
experiments, using 2 exclosures. *
indicates aggregated distribution, based on the statistical procedure of CLARKE &
MILNE (1955); otherwise, the distribution is random. Each mean and CD is based on 3 replicate 0.0048-m? cores.
Exclosure 1
Exclosure 2
Unprotected 1 Unprotected 2
Species Date x CD x
Mya 6/8 We) 0.9 8.0
6/23 Bild) 7.6* 19.3
UT 110.3 303% 44.0
7/20 42.0 39" 24.3
8/4 36.7 8.9* Del
Mulinia 6/8 48.7 2.3 86.0
6/23 142.7 B52" 168.3
7/7 90.7 0.6 96.0
7/20 Wo) 3.1 83.3
8/4 60.3 2.8 96.7
Gemma 6/8 169.3 205% ie
6/23 100.7 ON ee 74.3
Uf 110.0 5.6* 96.3
7/20 92.3 Ze ah
8/4 56.3 Spike Boe)
Linear regressions of Coefficient of Dispersion (y) on Mean (x):
Species Intercept Slope r’
Mya 0.86 0.23 0.810
Mulinia
All data —9.49 3.06 0.467
Less 2 highest 7.30 0.001 0.0003
Gemma 3.35 0.14 0.209
CD X CD x CD
Bul 10.0 5.3 ih ed/ 3.3
3)" 9.3 bea 5.7 Iai
4.1* 3)55) 1E9, 4.0 0.5
VL 0.0 os 8) 0.2
Noe 0.7 0.3 0.3 0.7
ND 35.3 2 33.0 D2
T23% 60.0 21.6* 82.3 516%
12.1* 59.3 i 68.0 4.1*
0.1 17.3 0.9 50.0 4.3*
0.8 39.3 16.1* 18.3 0.6
21.4* 100.3 ile Sic 24.7 7.6*
30.5* Bley Vol 18.0 6.7*
51.6* 22.0 2.8 44.0 Val
1.0 ALY 14.4* 19.3 2.1
0.8 1333) De, Si 30
(Say, 1822) (Mactridae)—and one with direct develop-
ment—Gemma gemma (Totten, 1834) (Veneridae).
MATERIALS anp METHODS
Field work was performed at the New Jersey Oyster Re-
search Laboratory on the Cape May shore of Delaware
Bay. Predator exclosures were 1.2 x 1.2 x 0.3 m wooden
frames covered top and sides with large mesh wire (5.1
cm hexagonal openings in 1978, or 5.0 x 10.0 cm rect-
angular openings in 1979) to exclude shorebirds, large
crabs, and fishes. The medium sand sediment (mean grain
size = 0.38 mm, with <1% silt-clay) was not significantly
altered by the cage (BOTTON, 1982).
To sample a cage, a 6-by-6 grid was painted on the
side of the frame, and the location of a core was deter-
mined by rolling two dice. In 1978, three cores were taken
from each of the two exclosures and three more from each
adjoining unprotected plot on 8 June, 23 June, 7 July,
20 July, and 4 August. In 1979, four cores were taken
from each of the three exclosures and from each unpro-
tected plot on 16 April, 24 May, 14 June, 6 July, 20 July,
and 3 August. Each cage plus its unprotected plot is here-
after referred to as a “‘site”; a distance of about 30 m
separated the sites. Cores were taken with a glass jar, 7.8-
cm inside diameter (=0.0048 m?’), which sampled to a
depth of 10 cm. This core size was chosen because (1) the
requisite number of replicates could be obtained without
disrupting adjacent sediments or re-sampling a previous
coordinate within the cage, and (2) prior qualitative sam-
pling had revealed the small sizes and high densities of
the infauna (see DOWNING [1979] on the relationship be-
tween benthos density, size of sampling devices, and num-
ber of replicates). Cores were washed through a 500-uwm
mesh sieve, and the material retained was fixed in 10%
formalin and transferred to 70% ethanol with rose bengal
stain. Bivalves were enumerated and measured to the
nearest 0.1 mm with an ocular micrometer or vernier cal-
iper.
The spatial distribution of bivalve populations within
sites was computed by the Coefficient of Dispersion (CD),
which is the variance/mean ratio. This measure is based
on the principle that for randomly distributed individuals,
the mean number of individuals per core should equal the
variance (Pielou, 1969). A CD significantly above one
indicates that the population is aggregated, and values
significantly less than one indicate a uniform dispersion.
Statistical significance was based on the test of CLARKE &
MILNE (1955), namely, a CD exceeding the confidence
interval 1 + 2\/(2n)/(n —1), where n is the number of
Page 284
replicate cores used to sample each caged or uncaged plot.
Bivalves with a CD within this boundary are considered
to be randomly distributed.
RESULTS
In 1978, caged sediments contained a significantly higher
density of individuals than uncaged sediments. This re-
sponse resulted from the enhanced survival of the bivalves
Mya arenaria, Mulinia lateralis, and Gemma gemma (Table
1, and BoTToN, 1984).
Mya arenaria was generally aggregated in cages, but
randomly dispersed in uncaged sediments. Only the 1978
year-class was present on 8 June, based on the size-fre-
quency distribution which showed a mean shell length less
than 2 mm, with no individuals >5 mm (BOTTON, 1984).
The spatial pattern of newly set M. arenaria was similar
regardless of treatment (Table 1). From 23 June onward,
M. arenaria was aggregated in all caged sediments, except
for exclosure 2 on 4 August. In contrast, the few Mya
surviving in unprotected sediments during July and Au-
gust were randomly distributed. Pooling both caged and
uncaged samples, most of the variability in the Coefficient
of Dispersion was related to the mean (linear regression,
r? = 0.81; Table 1).
Mulinia lateralis was even more abundant than Mya
arenaria, but did not show the same spatial pattern. Only
the 1978 year-class of Mulinia lateralis was present; when
first sampled (8 June), mean shell length was 1.5 mm,
and there were no individuals above 3 mm in length
(BoTTON, 1984). On 8 June, the day that cages were put
in place, M. lateralis was highly aggregated in three of the
four areas (Table 1). On 23 June, caged individuals of
M. lateralis were aggregated; on 7 July, only cage 2 was
aggregated, but on 20 July and 4 August, all caged M.
lateralis were randomly distributed. The responses of the
uncaged areas were not consistent. Overall, excluding 8
June, M. lateralis was aggregated in 6 of 8 uncaged sam-
plings, but only 3 of 8 caged samplings. There was a weak
positive relationship between CD and mean, as shown by
linear regression. When all data were considered, r? was
0.47; however, when the two highest means (168.3 and
142.7 individuals/core) were eliminated, r? was only
0.0003 (Table 1).
The spatial distribution of Gemma gemma was analyzed
in two ways: (1) the population as a whole, 1.e., by com-
bining all size classes (Table 1), and (2) separate analysis
of new recruits (<1.4 mm) and older individuals (>2.8
mm) (Table 2). In the first case, individuals of G. gemma
from both caged and uncaged sediments were most aggre-
gated early in the summer, 7.e., when clams were smaller
and more numerous. Only 21% of the variability in CD
was related to the population size (Table 1). The spatial
distribution of new set was most aggregated early in the
summer (Table 2). Larger G. gemma showed a mixture
of clumped and random distributions, regardless of treat-
ment.
The Veliger, Vol. 26, No. 4
The results from 1979 were limited to Gemma gemma,
because both Mya arenaria and Mulinia lateralis had near-
ly complete recruitment failures (BOTTON, 1984). On 16
April, there were few small G. gemma, as the population
consisted mainly of survivors from the 1978 year-class
(Table 2, and BoTTON, 1984). Large numbers of the 1979
year-class were retained on a 500-ym sieve from 14 June
onward, and small individuals of G. gemma were gener-
ally aggregated in both protected and unprotected sedi-
ments. Large G. gemma individuals in unprotected sedi-
ments were randomly distributed in 15 of 18 instances
(Table 2). In contrast, protected large G. gemma individ-
uals were clumped in 12 of 17 cases.
The mean coefficient of dispersal for small Gemma gem-
ma was 15.05 and for large G. gemma, 6.05. Protected
clams were more aggregated (mean CD = 14.51) than un-
protected clams (mean CD = 6.82) (Analysis of Variance,
F = 6.85, 1,5 df, P < 0.05).
DISCUSSION
Aggregation, as measured by the coefficient of dispersion
(variance/mean ratio), varies with mean density
(DowniNnG, 1979), but not all the variability in CD can
be explained by this alone; biological factors must be con-
sidered. The three species studied have important life-
history differences with respect to reproductive mode,
mobility, and vulnerability to predation and sediment dis-
turbance (Table 3). Gemma gemma, which has direct de-
velopment, may be considered as an “equilibrium” species,
somewhat resistant to predation (SCHNEIDER, 1978;
Woop, 1981). Mulinia lateralis and Mya arenaria, which
recruit by planktonic larvae, are “opportunists,” quite
vulnerable to predation (VIRNSTEIN, 1977; BOTTON, 1984).
The clumped distribution of small Gemma gemma found
in 1979 and the first month of 1978 is consistent with
JACKSON (1968). Older individuals of G. gemma were ran-
domly distributed in the unprotected areas in the 1979
study, in agreement with JACKSON (1968) and GREEN &
Hopson (1970), though THOMPSON (1982) found that most
G. gemma adults (defined as >0.9 mm length) on a San
Francisco Bay mudflat were aggregated. The aggregation
of larger G. gemma within exclosures may be imposed by
the clumping of newly released juveniles, and retained in
the absence of predation or sediment disturbance. The
Delaware Bay intertidal flats are unstable and are re-
worked by horseshoe crab burrowing; thus, individuals of
G. gemma are unlikely to remain in the vicinity where
they set. Yet, the clumped distribution of unprotected <1.4
mm animals throughout 1979 suggests that either distur-
bance did not completely randomize the spatial pattern,
or that continued release of juveniles overshadowed the
impact of disturbance. The importance of predation to
larger G. gemma is debatable, since several studies indicate
that this species is not preferred prey to certain shorebirds
(SCHNEIDER, 1978), crabs (WOODIN, 1981), or horseshoe
crabs (BOTTON, 1982), whereas GREEN & Hosson (1970)
M. L. Botton, 1984
Page 285
Table 2
Spatial distribution of newly recruited (<1.4 mm) and older (>2.8 mm) Gemma gemma in the 1978 experiment (2
exclosures) and 1979 experiment (3 exclosures). CD = coefficient of dispersion; * indicates aggregated dispersion. Each
mean and CD in 1978 was based on 3 replicate 0.0048-m? cores; 4 replicates were used in 1979. Sites 1 and 2 in 1978
were not the exact same location as 1979.
<1.4 mm clams
Protected Unprotected
Date Mean CD Mean CD
8 June 1978
Site 1 58.0 Tol 44.3 15.0*
Site 2 30.0 7.0* 1323 4.5*
23 June 1978
Site 1 6.7 Dol 18) 0.7
Site 2 4.7 3.6 1.0 0.0
7 July 1978
Site 1 3)8) 1.1 1.3 0.2
Site 2 558) 1.3 6.0 1.3
20 July 1978
Site 1 3.7 0.1 1.3 Dell
Site 2 4.7 0.9 4.7 0.6
4 August 1978
Site 1 1.3) 1.2 3.7 0.4
Site 2 6.3 3.2 4.3 1.4
16 April 1979
Site 1 0.3 1.0 0.3 1.0
Site 2 0.8 1.2 0.3 1.0
Site 3 0.3 1.0 0.5 0.7
24 May 1979
Site 1 0.5 2.0 2.0 2.0
Site 2 4.8 14.2* 7.8 AWe2s
Site 3 2.8 Ores 1.3 163
14 June 1979
Site 1 9) 0.7 6.5 4.6*
Site 2 35.0 105.2* 12.8 14.7*
Site 3 18.5 11.3 2.8 2.0
6 July 1979
Site 1 8.0 4.6* 13.5 1.5
Site 2 50.3 14.0* Dies) 10.7*
Site 3 29.0 D3 11323 3.6*
20 July 1979
Site 1 43.0 11529 47.7 4.3*
Site 2 147.0 54.0* 64.0 48.7*
Site 3 108.0 46.7* 41.5 5.1
3 August 1979
Site 1 200 vel 57.8 13.0*
Site 2 129.0 44.8” 105.3 IVES
Site 3 60.3 10.3* 60.5 IRS
‘Mean and CD not calculated because of the loss of one replicate.
and RECHER (1966) noted predation on this species by
horseshoe crabs and shorebirds, respectively. Even when
G. gemma individuals on the Cape May shore of Dela-
ware Bay were as numerous as 206,000/m? (late spring,
1980), L. polyphemus contained an average of only 4.1 G.
gemma per gut (BOTTON, 1982).
JACKSON (1968) found that Mulinia lateralis was ran-
>2.8 mm clams
Protected Unprotected
Mean CD Mean CD
0.0 — 0.3 0.7
0.0 = 0.0 oe
9.7 0.6 1.0 0.7
0.7 1.3 0.3 0.7
66.0 7.8* 7.0 EZ
BON) Pa Oh 9.3 4.6*
77.3 3.6 553 7.0*
58.7 0.6 8.3 2.0
49.0 bra 3.7 0.1
27.0 1.3 obi 2.5
4.5 1.3 5.5 2.5
ES: 2.5 DD 1.0
2.3 0.7 6.0 1.8
9.8 Hoi 7439) 0.7
9.3 25.0* 4.5 1.6
3.8 30)” 1.5
4.0 0.7 3.8 2.9*
14.3 10.1* 3.5 2.4
14.5 20.3* ap) Ne
6.0 1.9 5:5 123
2553, 20.3* 7.0 1.6
14.5 8.5* 8.3 2.4
Bee 14.5* 13.3 1.4
45.0 13.8* 15.8 10.4*
20.5 15.4* 11.8 USO
Bee oO 1285 0.7
53.8 8.8* 26.8 1.8
32.3 6.3* 15.5 2.3
domly distributed on the scale of 5 cm-by-5 cm replicates
within a 0.25-m? area, and considered this a logical con-
sequence of its reproduction by planktonic larvae. How-
ever, in the present study, the smallest M. lateralis indi-
viduals (those found in June, 1978) were the most
aggregated. A possible explanation for the randomization
in spacing among older caged clams could be movement
Page 286
The Veliger, Vol. 26, No. 4
Table 3
Life-history characteristics of the three principal bivalve species.
Characteristic Gemma gemma
Brooder; larvae re-
leased as fully
shelled embryos at
375 pm
Reproductive mode
Mobility Strong, active bur-
Mulinia lateralis
Planktotrophic; larvae
set at 210-230 um
Active; juveniles can
Mya arenaria References
SELLMER, 1966;
LOOSANOFF et al.,
1966
Planktotrophic; larvae
set at 200 um
Limited and decreases BRADLEY & COOKE,
rower “hop” to avoid with increasing size 1959; VIRNSTEIN,
crowding 1977; STANLEY,
1970
Vulnerability to Low; reburrowed High High BRADLEY & COOKE,
sediment disruption from 5-20 cm 1959; VIRNSTEIN,
I977/
Vulnerability to Low High High SCHNEIDER, 1978;
predation VIRNSTEIN, 1977;
of individuals from sediments packed with conspecifics
and Mya arenaria. I have no direct evidence that this oc-
curred, although VIRNSTEIN (1977) observed that M. lat-
eralis would “hop” along the substrate to avoid very dense-
ly populated areas. M. lateralis is a thin-shelled and
shallow-burrowing clam, making it vulnerable to preda-
tion; it is a favorite prey of horseshoe crabs (BOTTON,
1982) and blue crabs (VIRNSTEIN, 1977). Predation on
uncaged M. lateralis had an important numerical impact,
but it did not equalize the spatial distribution, as might
have been expected if predators were optimal patch users
(HUGHES, 1980).
Mya arenaria is not an active burrower, and juveniles
up to ~10 mm often retain a byssal attachment to sand
grains (personal observations). These factors may explain
the difference in spatial pattern between protected M. ar-
enaria and the more active Mulinia lateralis. Caged M.
arenaria individuals were generally aggregated whereas
M. lateralis assumed a random distribution after an ini-
tially clumped set. The spatial pattern of M. arenaria ju-
veniles may be maintained in larger clams in the absence
of perturbations. Few M. arenaria survived outside cages,
and horseshoe crab predation probably accounted for most
of the mortality (BOTTON, 1984). The randomization of
unprotected M. arenaria may largely be a numerical ar-
tifact, since as the mean decreases, the more likely it is
that a Poisson distribution (variance = mean) is ap-
proached (CLARKE & MILNE, 1955).
This study has shown the importance of predation, dis-
turbance, and life histories to the spatial pattern of bi-
valves, but several questions remain unanswered. One fac-
tor that has yet to be elucidated is the possible impact of
predation and disturbance on the spatial pattern of newly
set spat, z.e., during the interval between settlement and
“recruitment” onto a 500-um sieve. Secondly, aggregation
was defined on the basis of replicate core samples within
BoTTon, 1982
a small exclosure, but if “optimal patch use” predators
are operating in this system, they may be doing so on
patch scales larger than those studied here. There were
some large differences in Coefficient of Dispersion and/
or mean number of individuals between sites separated by
approximately 30 m. The cause of this variation is not
known: differences may have been the manifestation of
slight variations in hydrographic factors, subtle differ-
ences in the substratum, or in the case of uncaged sedi-
ments, differential mortality resulting from variations in
predation and/or disturbance pressure.
ACKNOWLEDGMENTS
I thank Dr. Harold H. Haskin, Director of the New
Jersey Oyster Research Laboratory, N.J. Agricultural
Experiment Station, for facilities and financial support,
and two reviewers for their constructive criticisms. Sup-
port from the James and Anna Leathem Fund of Rutgers
University is gratefully appreciated.
LITERATURE CITED
Botton, M. L. 1979. Effects of sewage sludge on the benthic
invertebrate community of the inshore New York Bight.
Estuarine Coastal Mar. Sci. 8:169-180.
Botron, M. L. 1982. Predation by adult horseshoe crabs,
Limulus polyphemus (L.), and its effect on benthic intertidal
community structure of breeding beaches in Delaware Bay,
New Jersey. Doctoral thesis, Rutgers Univ., New Bruns-
wick, New Jersey. 466 pp.
Botton, M. L. 1983. Effects of laughing gull and shorebird
predation on the intertidal fauna at Cape May, New Jersey.
Estuarine Coastal Shelf Sci. (in press).
Botton, M. L. 1984. The importance of predation by horse-
shoe crabs, Limulus polyphemus, to an intertidal sand flat
community. J. Mar. Res. (in press).
BRADLEY, W. H. & P. Cooke. 1959. Living and ancient pop-
ulations of the clam Gemma gemma in a Maine coast tidal
flat. Fish. Bull. 58:305-334.
M. L. Botton, 1984
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CLARKE, R. B. & A. MILNE. 1955. The sublittoral fauna of
two sandy bays on the Isle of Cumbrae, Firth of Clyde. J.
Mar. Biol. Assoc. U.K. 34:161-180.
DowninG, J. A. 1979. Aggregation, transformation, and the
design of benthos sampling programs. J. Fish. Res. Board
Can. 36:1454-1463.
GaGE, J. & A. D. GEEKIE. 1973. Community structure of the
benthos in Scottish sea-lochs. II. Spatial pattern. Mar. Biol.
19:41-53.
GREEN, R. H. & K. D. Hopson. 1970. Spatial and temporal
structure in a temperate intertidal community, with special
emphasis on Gemma gemma (Pelecypoda, Mollusca). Ecol-
ogy 51:999-1011.
HucGues, R.N. 1980. Predation and community structure. Pp.
699-728. In: J. C. Price, D. E. G. Irvine & W. F. Farnham
(eds.), The shore environment, Vol. 2: Ecosystems. Academ-
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Jackson, J. B. C. 1968. Bivalves: spatial and size-frequency
distributions of two intertidal species. Science 161:479-480.
LEVIN, L. A. 1981. Dispersion, feeding behavior and compe-
tition in two spionid polychaetes. J. Mar. Res. 39:99-117.
LoosanorF, V. L., H. C. Davis & P. F. CHANLEY. 1966. Di-
mensions and shapes of larvae of some marine bivalve mol-
luscs. Malacologia 4:351-435.
MATTHIESSEN, G. C. 1960. Intertidal zonation in populations
of Mya arenarza. Limnol. Oceanogr. 5:381-388.
Moors, S. F. & D. B. MCLAUGHLIN. 1978. Design of field
experiments to determine the ecological effects of petroleum
in intertidal ecosystems. Water Res. 12:1091-1099.
PiELou, E. C. 1969. An introduction to mathematical ecology.
Wiley-Interscience: New York. 286 pp.
RECHER, H. F. 1966. Some aspects of the ecology of migrant
shorebirds. Ecology 47:393-407.
SCHNEIDER, D. C. 1978. Equalization of prey numbers by
migratory shorebirds. Nature 271:353-354.
SELLMER, G. P. 1966. Functional morphology and ecological
life history of the gem clam, Gemma gemma (Eulamelli-
branchia: Veneridae). Malacologia 5:137-223.
SiH, A. 1982. Optimal patch use: variation in selective pressure
for efficient foraging. Amer. Natur. 120:666-685.
STANLEY, S. M. 1970. Relation of shell form to life habits of
the Bivalvia (Mollusca). Geological Society of America,
Memoir 125:1-296.
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ma (Bivalvia: Veneridae) in south San Francisco Bay, with
a comparison to some northeastern United States estuarine
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THORSON, G. 1966. Some factors influencing the recruitment
and establishment of marine benthic communities. Neth. J.
Sea Res. 3:267-293.
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and fishes on benthic infauna in Chesapeake Bay. Ecology
58:1199-1217.
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The Veliger 26(4):288-298 (April 2, 1984)
THE VELIGER
© CMS, Inc., 1984
Orientational and Anatomical Trends Related to
Detorsion among Prosobranch Gastropods!
by
LOUIS F. GAINEY, JR.
Department of Biological Sciences, University of Southern Maine, Portland, Maine 04103
AND a
CHARLES R. STASEK
Department of Biology, Sonoma State University, Rohnert Park, California 94928
Abstract. Extant prosobranchs were placed into three groups based upon (1) the angle between the
coiling axis of the shell and the antero-posterior axis of the foot during locomotion and retraction of
the animal into its shell, (2) the angle between pallial water currents and the antero-posterior axis of
the foot, (3) the relative proportions of the shell aperture, and (4) the manner in which the foot was
folded during retraction. In Condition I (archaeogastropods and lower mesogastropods) the shell axis
is at a 30 to 60° angle to the foot during locomotion and retraction, the pallial water currents are at a
60 to 85° angle to the foot, the shell aperture is nearly round, and the foot most often folds transversely
during retraction. In Condition II (higher mesogastropods and neogastropods) the shell axis is at a 0
to 10° angle to the foot during locomotion but a 30 to 80° angle during retraction, the pallial water
currents are at a 10 to 30° angle to the foot, the shell aperture is nearly round, but with a siphonal
notch, and the foot most often folds transversely during retraction. In Condition III (higher mesogas-
tropods and neogastropods) the shell axis is at a 0 to 10° angle to the foot during locomotion and
retraction, the pallial water currents are at a 0 to 20° angle to the foot, the shell aperture is elongate,
and the foot folds longitudinally during retraction.
INTRODUCTION
ALTHOUGH MUCH ATTENTION has been given to the ge-
ometry of gastropod shells, there has been relatively little
work on the more subtle functional and orientational re-
lationships of these secretions to the soft parts that produce
them and to the environments within which they exist.
NAEF (1913) was one of the first to investigate the ways
in which shells of different shapes are carried by the an-
imals secreting them, noting that shells of extant proso-
branchs are asymmetrically deposited in drawn-out, he-
lical patterns—the “typical” snail shapes. These he termed
anisostrophic shells, which are in contrast to primitive
isostrophic shells, such as those borne by the extinct bel-
lerophonts. In that group the whorls lay in a single plane.
Naef concluded that anisostrophic shells, in spite of their
‘ Publication No. 199 of the Tallahassee, Sopchoppy and Gulf
Coast Marine Biological Association.
asymmetry, are carried in balanced positions by two si-
multaneous adaptations. The first of these he termed reg-
ulatory detorsion, whereby the spire of the shell has be-
come shifted toward the posterior end of the animal; the
second is inclination, whereby the coiling axis has become
tilted upwardly from its original horizontal position.
Naef outlined some theoretical evolutionary steps lead-
ing to regulatory detorsion, and more recent authors, most
notable RisBEc (1955) and LINSLEY (1978a), observed that
in those gastropods with shell spires directed posteriorly,
regulatory detorsion approaches 90°. These are the more
highly evolved snails in which the coiling axis lies vir-
tually parallel with the longitudinal axis of the extended
foot (MORTON & YONGE, 1964).
The development of anisostrophy, and the related ap-
pearance of regulatory detorsion and inclination, was ac-
companied by profound alterations in the disposition and
anatomy of the pallial organs and reno-pericardial com-
plex (NaAEF, 1913; YONGE, 1947), primarily the reduction
L. F. Gainey, Jr. & C. R. Stasek, 1984
and final loss of the post-torsional right members of pre-
viously paired structures.
Beginning with Raup’s development of a mathematical
model for coiled shells (RAUP, 1961, 1966), there has been
a renaissance in the study of the functional morphology
of gastropod shells. VERMEIJ (1971) described the inter-
relationships between angle of inclination of the coiling
axis and adaptive diversity of shell form. He found that
the small angles of inclination characteristic of siphonate
gastropods are related to a diversity of shell shape greater
than that possible among more primitive forms with large
angles of inclination. GRAUs (1974) reported a latitudinal
gradient in the morphological diversity of shells and pos-
tulated that the greater diversity in tropical latitudes is a
function of increased availability of calcium carbonate for
shell deposition. LINSLEY (1977, 1978a, b) noted that gas-
tropods with large angles of inclination are detorted less,
better adapted to hard substrata, and have lower rates of
locomotion than do gastropods with low angles of incli-
nation. PALMER (1980) proposed that locomotion rates
and shell form are but two of several co-evolving adap-
tations to different habitats. MCNAIR e¢ al. (1981) found
that gastropods with elongate apertures have elongate feet
and are found primarily on soft substrata.
There has remained to be undertaken a systematic study
of the magnitudes of regulatory detorsion and of its phy-
logenetic trends within the orders of the Prosobranchia.
Moreover, relationships between regulatory detorsion, the
proportions of the shell aperture, and mode of folding of
the foot during retraction have not been considered by
prior investigators. The present report describes some of
the major evolutionary changes within the prosobranch
framework in relation to these parameters.
Preliminary results of this study were presented to the
American Society of Zoologists (GAINEY, 1979).
MATERIALS anp METHODS
Living specimens of prosobranchs were collected at the
following localities: Jupiter Inlet and Lantana Beach, Palm
Beach Co.; Missouri Key and Long Key, Monroe Co.;
Turkey Point and Alligator Point, Franklin Co. (all in
Florida); Cape Elizabeth, Cumberland Co., Maine; and
Bodega Bay, Sonoma Co., California. Additionally, living
Indo-Pacific specimens of 30 species were observed by the
Junior author while on an expedition to Fiji in 1973 (Ta-
ble 4). Precise angular measurements were not taken from
the Fijian species. However, the position of the coiling
axis of the shell with respect to the antero-posterior axis
of the foot during locomotion and during retraction of the
animal into the shell, as well as the manner in which the
foot was folded during retraction, were noted. These ini-
tial observations provided the framework for our subse-
quent, more precise, measurements.
The following parameters were observed in living, adult
specimens:
(1) The locomotion angle is the angle formed between
Page 289
the antero-posterior axis of the foot and the coiling axis
of the shell, projected onto the horizontal plane (Figure
1A). The locomotion angle was measured from above a
snail as it crawled on a horizontal surface.
(2) The retraction angle is that formed between the lon-
gitudinal axis of the foot and the coiling axis of the shell
after retraction of the animal into its shell (Figure 1B).
Where the locomotion angle and retraction angle differ in
a species, the retraction angle represents the degree of
twisting of the shell relative to the median plane of the
body after withdrawal. As a matter of practicality, the
retraction angle was often measured as the head and foot
emerged from the shell cavity. Either mode of observation
yielded the same angular measurement.
(3) The water-current angle is the angle between the
inhalant pallial water current and the longitudinal axis
of the foot (Figure 1A). In species with siphonal notches
in the shell, the angle was calculated from a line connect-
ing inhalant and exhalant regions of the aperture; for
forms with apertures that lack notches, the water-current
angle was observed and measured with the aid of fine
particles of graphite or carmine placed in the water sur-
rounding the living specimens.
(4) The proportions of the shell aperture (b/a) were mea-
sured as follows: the “length” of the aperture (b) is the
greatest linear dimension in an abapical-adapical direc-
tion, excluding the siphonal notch (Figure 1C); the “width”
(a) is the greatest linear dimension perpendicular to the
“length” of the aperture. As a result of procedural differ-
ences, the aperture ratios reported here are slightly larger
than those described by VERMEIJ (1971). He defined ‘‘b”
as the greatest linear dimension of the aperture coplanar
with the coiling axis, and “a” as the greatest linear di-
mension perpendicular to “b.” Our measurements relate
to the full functional extent of the area passed through by
the soft parts as they expand from and contract into the
shell cavity. The dimensions of apertures of small species
were measured with the aid of camera lucida drawings of
the apertures.
(5) The manner in which the foot is folded during re-
traction into the shell was also noted (Figure 1B). Lon-
gitudinal folding refers to creasing of the foot along its
longitudinal axis. Transverse folding refers to creasing of
the foot along a line at right angles to its longitudinal axis
and perpendicular to the plane of the sole.
OBSERVATIONS
We discerned three distinct arrangements in the orienta-
tions of shell and body among the prosobranchs we ob-
served:
First, there was a group in which the coiling axis of
the shell forms a wide angle with respect to the median
plane of the head and foot. This angle is typically about
60°, and does not alter upon retraction of the body into
the shell cavity.
Second, there was a group in which the coiling axis is
Page 290
A
The Veliger, Vol. 26, No. 4
ff
—h
Figure 1
Orientational and anatomical parameters measured on living gastropods.
A: la, locomotion angle; wea, water current angle.
B: ra, retraction angle; ff, foot folding (transverse in this example); h, head; f, foot; 0, operculum.
C: aperture ratio, b/a.
Solid arrow shows inhalant current; open arrow shows exhalant current. Solid lines mark antero-posterior axes of
foot; dashed lines with terminal dots mark coiling axes.
parallel to, or forms an acute angle with, the median plane
of the head and foot. This orientation is altered dramati-
cally upon retraction.
Third, there was a group in which the coiling axis is
virtually parallel to the median plane of the foot, an ar-
rangement that does not alter upon retraction.
These situations form the basis for recognition of three
conditions that involve not only shell-body orientations,
but also the pallial water currents, proportions of the ap-
erture, and modes of folding of the foot.
Condition I
All species exhibiting Condition I are archaeogastro-
pods and non-siphonate mesogastropods (Tables 1, 4).
Locomotion and retraction angles are the same and fell
between 30 and 60°. That is, during locomotion the shell
is carried obliquely at a fairly constant orientation with
respect to the foot axis, and upon retraction the body and
shell do not twist relative to one another.
There are two major arrangements with respect to cte-
nidial water currents. Most trochaceans possess incurrent
and excurrent siphons formed by epipodial lobes, the for-
mer to the left, the latter to the right of the head. The
angle between inhalant and exhalant streams is approxi-
mately 120°. In the remaining groups, the inhalant and
exhalant water currents lie in a virtual straight line, which
formed an angle ranging from 70 to 85° with respect to
the longitudinal axis of the foot. Except for Viviparus,
epipodial siphons are lacking in these forms.
Aperture ratios ranged from 0.9 to 1.8; thus, the ap-
erture is broadly open. Among the archaeogastropods the
aperture ratios averaged 1.2, whereas among the meso-
gastropods the average was 1.4.
The foot typically folds transversely as it is withdrawn
into the shell aperture. There are exceptions (Figure 2a-
d). In Astraea longispina and Turbo castanea the foot is
withdrawn without folding. In Calliostoma jujubinum,
Tectus maximus, T. pyramis, and Trochus maculatus the
foot folds longitudinally. Among the latter three species,
the folded ventral surface of the foot faces the outer shell
lip at various angles, which affects the use or lack of use
of the operculum in blocking the aperture.
Condition II
Many siphonate mesogastropods and some neogastro-
pods are characterized by Condition II (Tables 2, 4).
Among the mesogastropods, locomotion angles ranged from
0 to 40° (average 12°) and retraction angles from 30 to
L. F. Gainey, Jr. & C. R. Stasek, 1984
Table 1
Species of gastropods typifying Condition I.
Locomotion
Animals angle
ARCHAEOGASTROPODA
Trochidae
Tegula funebralis (A. Adams, 1855) 60°
Calliostoma jujubinum (Gmelin, 1791) 60°
Turbinidae
Turbo castanea Gmelin, 1791 50°
Astraea americana (Gmelin, 1791) 50°
Astraea phoebia Roding, 1798 60°
Astraea tuber (Linné, 1767) SEP
Neritidae
Neritina reclivata (Say, 1822) 60°
Neritina virginea (Linné, 1758) 60°
Nerita tessellata Gmelin, 1791 60°
Nerita versicolor Gmelin, 1791 60°
MESOGASTROPODA
Vivipariidae
Viviparus malleatus Doe
Littorinidae
Littorina littorea (Linné, 1758) 60°
Littorina lineolata Orbigny, 1840 60°
Littorina ziczac (Gmelin, 1791) 60°
Littorina angulifera (Lamarck, 1822) 30°
Nodilittorina tuberculata (Menke, 1828) 60°
Tectarius muricatus (Linné, 1758) 60°
Modulidae
Modulus carchedonius (Lamarck, 1822) 60°
60° (average 52°). Among the neogastropods, the loco-
motion angles ranged from 0 to 10° (average 2°) and the
retraction angles from 30 to 80° (average 60°). In every
species, the locomotion and retraction angles are un-
equal—there is a twist of the shell as the body retracts
into its cavity. This twist is counterclockwise when the
animal is viewed from above.
Those species that carry the shell with its axis sub-
parallel to the locomotion angle (e.g., Planaxis lineatus)
bear a short siphonal notch. The inhalant siphon, which
extends from the notch, is carried in front of the head, or
else is actively swept in an arc from side-to-side in front
of the head during locomotion. Most of the species char-
acterized by Condition II are capable of moving their shells
in wide arcs during locomotion. This movement allows
water to be drawn into the mantle cavity from a variety
of directions and to “zero in” on sources of olfactory stim-
uli. In every case, water leaves the mantle cavity on the
posterior right side of the organism.
The water-current angles listed in Table 2 were mea-
sured from specimens while their shells were being carried
at the locomotion angles. The range of the water-current
angles among the mesogastropods was 15 to 31° (average
24°), whereas among the neogastropods the range was 10
Page 291
Water-
Retraction current Aperture Foot
angle angle ratio folding
60° 60° 1.1 transverse
60° 60° 1:3, longitudinal
50° 60° te none
50° 63° 1.2 longitudinal
60° 60° 0.9 none
558 60° 1 none
60° US? 1.5 transverse
60° 1.4 transverse
60° 80° iol transverse
60° 70° EZ transverse
55g 85° 1.4 transverse
60° 80° 16S transverse
60° 1e3 transverse
60° 1.6 transverse
30° 1.4
60° 1.3 transverse
60° 1.3 transverse
60° 1S transverse
to 30° (average 15°). Although all species of Condition II
are siphonate, the Potamididae lack a siphonal notch in
the shell aperture.
The aperture ratios in these organisms ranged from 1.2
in Urosalpinx perrugata to 2.2 in Terebra dislocata, the
average among the mesogastropods being 1.6, that among
neogastropods 1.5.
During retraction into the shell cavity the foot typically
folds once in the transverse plane (Figure 2f, 1). Among
the exceptions (Figure 2g, j-o0) are Cantharus cancellarius,
in which the foot is folded longitudinally, and species of
Terebra. There is no folding in Terebra dislocata or in T.
duplicaria, whereas in Terebra maculata and T. dimidiata
there is an oblique folding of the foot.
Condition III
Some mesogastropods and some neogastropods repre-
sent Condition III (Tables 3, 4), characterized by a per-
manent disposition in which the coiling axis of the shell
is subparallel to the longitudinal axis of the foot, whether
during locomotion or after retraction.
On the average, the inhalant current enters the mantle
cavity at 5° to the midline of the foot in the mesogastro-
Page 292
Zz
O
E
O
Zz
O
O
The Veliger, Vol. 26, No. 4
Figure 2
Some foot-folding patterns observed among prosobranchs; ventral views of sole. Anterior ends are upward in the
diagrams. In instances of multiple creases, the anterior portions fold first upon retraction. Within each category,
the presumed primitive state is shown first. a—(transverse) Tegula, Nerita; b—(longitudinal) Tectus, Calliostoma;
c—(three flaps) Nerita; d—(no folding) some Turbinidae; e—Vivipariidae, Littorinidae, Naticidae, etc., f—Ceri-
thidea, Cerithium, Cymatium; g—Bursidae (unident. sp.); h—Contumax nodulosus; i— Murex, Thais, Nassarius, Fascio-
laria; j—Nassarwus arcularius (with lateral crumpling); k—Cantharus; 1—Latirus (two lappets); m—Terebra (unident.
sp.); n—Terebra maculata, T. dimidiata; o—Duplicaria duplicaria, Terebra dislocata; p—Cypraeidae, Cassididae; q—
Columbellidae, Olividae, etc.; r—Conus litteratus, Mitridae; s—Conidae.
pods, 14° in the neogastropods, and forms a virtual straight
line with respect to the exhalant current, which is located
far posteriorly on the right side of the body.
The shell aperture is always much longer than wide,
the ratio averaging 6.7 for mesogastropods and 4.6 for
neogastropods. The foot never folds transversely (Figure
2p-s), but either creases longitudinally or, as in species of
Conus, simply slips unfolded along the columella into the
shell cavity with the sole facing the outer lip of the shell.
We have not incorporated into our research a study of
the operculum. However, it should be noted that the size
of this structure, where present, and its position upon the
foot are closely related to folding of the foot and to pro-
portions of the aperture. In species with transverse fold-
ing, the operculum is attached to the section posterior to
the fold, which retreats last into the aperture. This ar-
rangement ensures closure of the opening by the opercu-
lum. Among forms with narrow apertures and longitu-
L. F. Gainey, Jr. & GC. R. Stasek, 1984
Table 2
Species of gastropods typifying Condition II.
Locomotion
Animals angle
MESOGASTROPODA
Potamididae
Batillaria minima (Gmelin, 1791) 0°
Cerithidea costata (daCosta, 1778) 0°
Cerithiidae
Cerithium eburneum Bruguiére, 1792 0-40°
Cerithium muscarum Say, 1832 0°
Planaxidae
Planaxis lineatus (daCosta, 1778) 30°
Cymatiidae
Cymatium parthenopeum (von Salis, 1793) 0°
NEOGASTROPODA
Muricidae
Murex florifer A. Adams, 1855 0°
Urosalpinx perrugata (Conrad, 1846) o°
Thais rustica (Lamarck, 1822) 0°
Nucella emarginata (Deshayes, 1839) 0°
Nucella lapillus (Linné, 1758) BP
Buccinidae
Cantharus cancellarius (Conrad, 1846) 0°
Melongenidae
Melongena corona (Gmelin, 1791) 0°
Busycon contrarium (Conrad, 1840) 0°
Nassariidae
Ilyanassa obsoletus (Say, 1822) 10°
Nassarwus vibex (Say, 1822) 10°
Fasciolariidae
Fasciolaria hilum hunteria (G. Perry, 1811) 0°
Terebridae
Terebra dislocata (Say, 1822) 0°
dinal foot-folds, the operculum is generally reduced or
lacking. Independent trends toward reduction and loss of
the operculum have taken place both in the mesogastro-
pods (Cassididae, Cypraeidae) and in the neogastropods
(Conidae, Mitridae) of Condition III.
CONCLUSIONS anp DISCUSSION
Observed prosobranchs fall into any one of three anatom-
ical groups, here termed Conditions I, II, and III. Each
condition is composed of features that may be analyzed
separately, but are here interpreted as having evolved in
closely interrelated fashions. Of the qualities concerned,
orientation of the shell axis with respect to the extended
foot, presence or absence of a twist of the shell over the
foot during its retraction into the shell cavity, and the
angle formed between pallial water currents and the axis
of the foot were considered of primary importance in plac-
ing species in one of the three conditions. The relative
proportions of the aperture and the manner in which the
foot folds were considered of secondary importance, be-
Page 293
Water-
Retraction current Aperture Foot
angle angle ratio folding
60° 30° 5) transverse
30° 31° EZ, transverse
50° 30° 123) transverse
60° 30° 1.3 transverse
60° 152 1.8 transverse
60° 153 1.5 transverse
60° 10° 1.4 transverse
60° 10° eZ transverse
60° 20° 2 transverse
60° 10° 185 transverse
Oz 10° 1.7 transverse
30° 10° 1.7 longitudinal
80° 10° 1.4 transverse
70° 10° ley transverse
60° 20° 1.4 transverse
40° 20° 1.4 transverse
60° Sg 2 transverse
60° 20° DO, none
cause there are overlaps and exceptions among these qual-
ities within the three conditions. Typical arrangements
are illustrated in Figure 3.
To set an evolutionary context for our observations, we
agree with the view that modern gastropods found their
origins in an extinct superfamily of archaeogastropods, the
Bellerophontacea (Figure 3; see STASEK, 1972:26). These
primitive forms were isostrophic and have been deduced
to have possessed two bipectinate ctenidia, and hence paired
reno-pericardial organs (NAEF, 1913; YONGE, 1947). The
locomotion and retraction angles were probably 90°; that
is, detorsion would have been 0° (Figure 3). There would
have been no twist of the shell over the body during re-
traction. Moreover, the aperture ratio would have been
low, a conclusion reached from illustrations in KNIGHT et
al. (1960). If the foot folded at all during retraction, it
was probably transverse to the longitudinal axis. Thus,
based upon the parameters that define existing proso-
branchs of Conditions I, II, and III, the bellerophonts
would form another group—Condition “0” (Figure 3).
Steps away from bellerophont shell morphology in-
Page 294 The Veliger, Vol. 26, No. 4
zZ
©
=
a
Z
O
O
Figure 3
Summary of conditions relating locomotion, retraction, and water-current angles, aperture ratios, and foot folding
among the prosobranch orders. Measurements are rounded-off averages from Tables 1, 2, and 3, except for the
locomotion angle and retraction angle among the neogastropods of Condition III, for which measurements from
Mitrella lunata have been excluded. Aperture ratios are indicated by ovals, not by outlines of actual apertures.
Dotted outlines in Condition II represent the extent of twisting of the shell over the body upon retraction of the
foot. The bellerophonts are represented in Condition “0” by Knightites multicornutus (modified from Cox, 1960:
195). Solid arrows show inhalant currents; open arrows show exhalant currents. Solid lines mark antero-posterior
axes; dashed lines with terminal dots mark coiling axes. L, longitudinal folding; T, transverse folding of the foot.
L. F. Gainey, Jr. & C. R. Stasek, 1984
Table 3
Species of gastropods typifying Condition III.
Locomotion
Animals angle
MESOGASTROPODA
Eratoidae
Trivia pediculus (Linné, 1758) 0°
Ovulidae
Simnia uniplicata (Sowerby, 1848) 0°
Cassididae
Cassis tuberosa (Linné, 1758) 0-10°
NEOGASTROPODA
Columbellidae
Columbella rusticoides Heilprin, 1887 o°
Mitrella lunata (Say, 1826) 10°
Olividae
Oliva sayana Ravenel, 1834 0°
Olwella pusilla (Marrat, 1871) 0252
Marginellidae
Marginella apicina Menke, 1828 0°
Conidae
Conus floridanus Gabb, 1868 0°
Turridae
Cryoturris cerinella (Dall, 1889) 0°
volved the formation of a spired shell, inclination of the
coiling axis, and regulatory detorsion (NAEF, 1913; YONGE,
1947; LINSLEY, 1977). These qualities are borne by Pleu-
rotomaria, regarded on anatomical grounds as among the
most primitive living archaeogastropods. We have not ob-
served Pleurotomaria, but we predict that it will have a
locomotion angle of 60°, a shell and body that do not twist
relative to one another during retraction, and a foot that
folds transversely upon withdrawal into the shell cavity.
These qualities would make Pleurotomaria a basic repre-
sentative of Condition I.
The elements that comprise Condition I are found
among recent non-patelliform archaeogastropods and non-
siphonate mesogastropods. These animals are similar in
their general appearance: detorsion ranges from 30 to 60°,
and all of them have a rather high angle of inclination of
the coiling axis (VERMEIJ, 1971). Moreover, most of them
are grazers that are, with few exceptions, restricted to
hard substrata. Based upon accepted views of gastropod
phylogeny, we conclude that the qualities that define Con-
dition I are primitive. To date, we have observed no neo-
gastropods with the conformation of Condition I.
The mesogastropods and neogastropods characterized
by Condition II bear shells the coiling axes of which are
carried virtually parallel to the longitudinal axis of the
extended foot. The inhalant and exhalant streams lie in a
straight line, with the inhalant position much closer to the
midline of the head than in forms typified by Condition
I. These orientations alter upon retraction of the foot into
the shell cavity in that the coiling axis swings counter-
Page 295
Water-
Retraction current Aperture Foot
angle angle ratio folding
0° 0° 9 longitudinal
0° 0° 4 longitudinal
0-10° 15° Wo longitudinal
0° ile 5) longitudinal
10° 16° 2 longitudinal
0° 6° 5:3 longitudinal
0° 20° 3.1 longitudinal
0° 10° 6.7 longitudinal
0° 152 7.8 longitudinal
0° 20° 2 longitudinal
clockwise when viewed from above. The twist of an av-
erage mesogastropod is about 40°; the shell moves even
more, on the average, among the neogastropods. The
species of Condition II are permanently detorted to about
the same degree as those of Condition I, and temporarily
detorted during locomotion by an additional 40 to 58° in
mesogastropods and neogastropods, respectively. The ori-
entation of the two axes in the retracted state is practically
identical to the permanent arrangement of the more prim-
itive forms characterized by Condition I.
As in Condition I, transverse folding of the foot during
retraction is regarded as primitive, and the proportions of
the length to width of the aperture of the shell are about
the same as, or only slightly longer with respect to width,
than those typical of Condition I. Species of Terebra are
more variable in the matter of foot-folding than those of
any other genus observed (Figure 3m, n, 0).
Mechanisms relating to unequal locomotion and re-
traction angles vary within Condition II. In species with
fusiform shells, the siphon is brought to an anterior po-
sition by muscular action, whereas species with high-spired
shells that taper to slender points employ a purely passive
mechanism (such as dragging on or in the substratum) to
bring the siphon around in front (GAINEY, 1976). Consid-
ering PONDER’S (1973) views on gastropod phylogeny,
there has been convergent evolution of both fusiform and
high-spired shells among mesogastropods and neogastro-
pods.
The functional significance of high-spired shells is un-
clear. GRAUS (1974) noted that shells of this kind are
Page 296
Table 4
The Veliger, Vol. 26, No. 4
Fijian species observed in relation to Conditions I, II, and III.
Archaeogastropoda
Trochidae
Trochus maculatus
Tectus maximus
T. pyramis
Neritidae
Nerita spp.
Condition I
Condition II
Condition III
usually confined to burrowing species, and he speculated
that drag would be reduced as a result of elongation in
the direction of locomotion. VERMEIJ (1977, 1978) ob-
served that an increase in spire height reduces predation
by calappid crabs, and that the appearance of antipreda-
tory features of gastropod shells in the Mesozoic was par-
alleled by an increase in their predators. High-spired shells,
for example those of the extinct Murchisoniacea and Lox-
onematacea, thought to be ancestral to the Cerithiacea
(Cox, 1960:143), are known from the Paleozoic, which
would seem to preclude a solely antipredatory function of
the shells of those groups.
The mesogastropods and neogastropods of Condition
III exhibit a greater departure from the ancestral form
than do those of Condition II. The temporary virtual
alignment of shell and foot characteristic of Condition II
is here permanent, with no twisting upon retraction. The
angle at which the water current enters the mantle cavity
with respect to the median plane is much more acute in
the mesogastropods of Condition III, less so in the neo-
gastropods. In keeping with the elongate apertures, which
may be as much as nine times longer than wide, the foot
Mesogastropoda
Littorinidae
Littorina sp.
Naticidae
Polinices pyriformis
Cerithiidae
Contumax nodulosus
Cerithium sp.
Neogastropoda
Thaididae
Mancinella mancinella
Morula granulata
Bursidae Nassariidae
“Bursa” sp. Nassarws arcularius
Fasciolariidae
Latirus gibbulus
Terebridae
Terebra maculata
T. dimidiata
Duplicaria duplicaria
Ovulidae Olividae
Volva sp. Oliva mustellina
Cypraeidae Mitridae
Cypraea tigris
Mitra mitra
Vexillum sanguisugum
V. vulpecula
V. gruneri
Neocancilla papilio
Pterygia dactylus
Conidae
Conus liratus
C. arenata
C. litteratus
C. ebraeus
folds longitudinally as it is withdrawn, or slips unfolded
into the shell cavity with the sole of the foot facing the
outer shell lip. Again, there have been parallel evolution-
ary trends of these factors among mesogastropods and neo-
gastropods. An additional factor in such parallelism has
involved the probable independent appearance in the two
higher prosobranch orders of inhalant siphons and of si-
phonal notches in their shells (PONDER, 1973).
FRETTER (1965) concisely summarized the anatomical
arrangements found among the Prosobranchia, noting two
major grades of organization—the Diotocardia, which we
here term the Archaeogastropoda, and the Monotocardia,
which is composed of the Mesogastropoda and Neogas-
tropoda. Each of the latter two groups was considered by
Fretter to represent an additional grade of organization.
The conditions recognized in the present paper may also
be considered grades of organization, but referring pri-
marily to orientational relationships, rather than to ana-
tomical conditions, as are those described by Fretter. Thus,
Figure 3 represents a cross-indexing of anatomical grades
in the vertical columns and orientational grades along the
horizontal axis.
L. F. Gainey, Jr. & C. R. Stasek, 1984
We have, then, the anatomical grade of the Archaeo-
gastropoda, within which anatomical and orientational bi-
lateral symmetry of the bellerophonts was lost through
suppression of the post-torsional members of several pre-
viously paired organ systems and through the appearance
of anisostrophy.
It was with the shell and body disposed in the orzenta-
tional grade of Condition I that the Prosobranchia evolved
the higher anatomical grades of organization: the mono-
pectinate ctenidium, as well as the complete loss of right
members of the pallio-renopericardial complex and the
straightening out of the water currents. The primary taxo-
basis used by many to delineate the Mesogastropoda, the
taenioglossate radula, made its appearance among forms
characterized by Condition I.
Subsequent alterations in orientational relationships (that
is, the temporary situation of Condition II and the per-
manent reorganization toward permanent external bilat-
erality of Condition III) took place independently within
each of the higher two grades of anatomical organization.
One, the Mesogastropoda, is extremely diverse, but with
many herbivorous groups; the Neogastropoda consists
mainly of carnivorous forms. Mode of feeding is, there-
fore, independent of orientational relationships, not only
in Conditions II and III, but also in Condition I. It was
with that primitive organization that the carnivorous Na-
ticidae made their appearance.
There was, in the earlier stages of both the mesogas-
tropods and neogastropods, some slight narrowing of the
apertures (Condition II); but, independently in both those
orders, the apertures became greatly elongated adapically-
abapically. There are several functional advantages that
have been proposed for this elongation. For example, in
the Conidae, Olividae, Volutidae, and Mitridae, various
aspects of shell form, including an elongate aperture and
foot, have been seen as adaptations to living on or in soft
substrata (GRAUS, 1974; MCNAair et al., 1981). VERMEIJ
(1978, 1979) has presented extensive and convincing evi-
dence that elongate shell apertures are particularly effec-
tive as a means of reducing predation, especially by crabs.
It seems probable to us, as is the case in high-spired shells,
that there are several adaptive advantages operating with-
in the same species that would select for the traits char-
acteristic of Condition III.
Finally, the primitive situation whereby the foot folds
transversely during retraction into a broadly rounded ap-
erture is replaced in both the mesogastropods and neo-
gastropods by an elongate foot that either folds longitu-
dinally or slips unfolded into a long, narrow aperture.
Orientation of the shell in relation to the body, positions
of inhalant and exhalant water currents, retractory mech-
anisms of the foot, and proportions of the aperture of the
shell have been shown to be interrelated attributes of gas-
tropod functional anatomy. That the observed arrange-
ments within any one order comprise a system of co-evolv-
ing elements is indicated by the parallelism that exists
within the independent lineages of the Mesogastropoda
Page 297
and Neogastropoda. At the same time that this clarifies
some of the major evolutionary trends within the subclass
Prosobranchia, we do not wish to imply “straight-line”
phylogenies: that there has been convergent evolution and
perhaps polyphyly finds much support. Yet, observed cor-
relation of multiple traits reveals that we are dealing with
matrices of co-evolving qualities, both anatomical and ori-
entational.
ACKNOWLEDGMENTS
The senior author wishes to thank Dr. Michael J. Green-
berg for providing space at Florida State University dur-
ing the early phases of this project. He would also like to
thank his wife, parents, and sister for assistance in col-
lecting specimens. The junior author wishes to express his
appreciation to Dr. Steven A. Wainwright, Duke Uni-
versity, for his support during the Fiji expedition in 1973.
LITERATURE CITED
Cox, L. R. 1960. Gastropoda: general characteristics of Gas-
tropoda. Pp. 84-169. In: R. C. Moore (ed.), Treatise on
invertebrate paleontology. Part I. Mollusca 1. Geological
Society of America: Boulder, Colorado. i-xxili + 351 pp.
FRETTER, V. 1965. Interrelations of monotocardian gastro-
pods. Proc. First European Malacology Congress: 55-59.
GaINEY, L. F., JR. 1976. Locomotion in the Gastropoda: func-
tional morphology of the foot in Neritina reclivata and Thais
rustica. Malacologia 15:411-431.
GaINEY, L. F., JR. 1979. Detorsion in prosobranch gastropods.
Amer. Zool. 19(3):1009.
Graus, R. R. 1974. Latitudinal trends in the shell character-
istics of marine gastropods. Lethaia 7:303-314.
KNIGHT, J. B., L. R. Cox, A. M. KEEN, R. L. BATTEN, E. L.
YOCHELSON & R. ROBERTSON. 1960. Systematic descrip-
tions. Pp. 169-331. In: R. C. Moore (ed.), Treatise on in-
vertebrate paleontology. Part I. Mollusca 1. Geological So-
ciety of America: Boulder, Colorado. i-xxiii + 351 pp.
LINSLEY, R. M. 1977. Some “laws” of gastropod shell form.
Paleobiology 3:196-206.
LINSLEY, R. M. 1978a. Locomotion rates and shell form in
the Gastropoda. Malacologia 17:193-206.
LINSLEY, R. M. 1978b. Shell form and the evolution of gas-
tropods. Amer. Sci. 66:432-441.
McNair, C. G., W. M. Kier, P. D. LACRoIx & R. M. LINSLEy.
1981. The functional significance of aperture form in gas-
tropods. Lethaia 14:63-70.
Morton, J. E. & C. M. YonGE. 1964. Classification and
structure of the Mollusca. Pp. 1-58. In: K. M. Wilbur &
C. M. Yonge (eds.), Physiology of Mollusca. Vol. 1. Aca-
demic Press: New York. i-xiii + 473 pp.
Naer, A. 1913. Studien zur generellen Morphologie der Mol-
lusken. 1. Ergebnisse und Fortschritte der Zoologie 3:73-
164.
PALMER, A. R. 1980. Locomotion rates and shell form in the
Gastropoda: a re-evaluation. Malacologia 19:289-296.
PONDER, W. F. 1973. The origin and evolution of the Neo-
gastropoda. Malacologia 12:295-338.
Raup, D. M. 1961. The geometry of coiling in gastropods.
Proc. Natl. Acad. Sci. 47:602-609.
Raup, D. M. 1966. Geometric analysis of shell coiling: general
problems. J. Paleontol. 40:1178-1190.
Page 298
RIsBEC, J. 1955. Considérations sur |’anatomie comparée et la
classification des gastéropodes prosobranches. J. de Conch.
15:45-82.
STASEK, C. R. 1972. The molluscan framework. Pp. 1-44. In:
M. Florkin & B. Scheer (eds.), Chemical zoology, Vol. VII.
(Mollusca). Academic Press: New York, N.Y. i-xxi + 567
VERMEIJ, G. J. 1971. Gastropod evolution and morphological
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15-23.
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VERMEIJ, G. J. 1977. The mesozoic marine revolution: evi-
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VERMEIJ, G. J. 1978. Biogeography and adaptation. Harvard
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The Veliger 26(4):299-304 (April 2, 1984)
“andi wae
© CMS, Inc., 1984
Reproductive Cycle of Anomia simplex
(Pelecypoda: Anomiidae) from
Cape Cod, Massachusetts
DIANE J. BROUSSEAU
Department of Biology, Fairfield University, Fairfield, Connecticut 06430
Abstract. Anomia simplex from Woods Hole, Massachusetts, were studied for 24 months to deter-
mine the sequence of gametogenic development of gonadal tissue and the frequency and duration of the
spawning cycle under natural conditions. These bivalves were observed to spawn annually in June-
August after undergoing rapid gametogenesis. Sexes were distinguishable in all individuals examined,
except those reported in an “inactive” condition. A low incidence of hermaphroditism suggests that
Anomia simplex is a stable gonochoric species. Sex ratios of A. sumplex did not differ significantly from
1:1 suggesting that protandry does not exist in this species. Photomicrographs of the gametogenic cycles
of both male and female mussels are included.
INTRODUCTION
Anomua simplex (Say), the jingle shell, is a common bivalve
of shallow waters from Nova Scotia to the West Indies.
The valves of A. semplex are nearly translucent and, unlike
most bivalves, they live permanently attached to solid ob-
jects by means of a stalklike byssus that passes through
an opening in the lower valve. The cuplike upper valve
commonly washes ashore after the animal dies and is one
of the most abundant shells on many beaches. To date,
the only information available on any aspect of the biology
of Anomia simplex is COE’s (1943a) histological study de-
scribing development of the primary gonads.
This study was designed to (1) define and categorize
the sequence of gametogenic development based on micro-
scopic examination of gonadal tissue and (2) determine
the frequency and duration of the spawning cycle of A.
simplex in a natural setting.
MATERIALS anpD METHODS
Specimens of Anomia simplex were obtained from the Ma-
rine Biological Laboratory Supply Department, Woods
Hole, Massachusetts. Individuals were obtained once a
month during July, October, December 1981, February
through September 1982, November 1982, and January
through April 1983; twice a month during May 1983;
three times in June 1981 and four times in August 1981.
Sample sizes ranged from 10 to 20 individuals of variable
shell size. A total of 412 bivalves was examined, of which
9 were immature. The remaining 403 mature individuals
were used in the analysis of the reproductive cycle.
In the laboratory, the visceral mass of each individual
was removed and fixed in 10% buffered formalin
(HuMASON, 1967). The tissues were then prepared for
histological examination (BROUSSEAU, 1978). A micro-
scopic examination was made to assign each individual to
the appropriate category of gonadal condition. Gonad col-
or ranged from cream to dark orange, the darker shades
appearing during the reproductively active months of the
year. Photomicrographs of representative stages of the male
and female reproductive cycle were taken with a Zeiss
light microscope at 190 using a 35-mm camera. Pana-
tomic X (ASA 32) film was used.
Mean oocyte diameter was determined for ten ripe fe-
males selected at random from each of the reported
spawning periods. Twenty oocytes per individual were
measured using an ocular micrometer. Only those oocytes
that were spherical in shape and ready for release were
selected for measurement.
The reproductive condition of the bivalves was mea-
sured by stereology, a procedure adapted by BAYNE et al.
(1978) and NEWELL et al. (1982). This method is based
on a procedure referred to as point-counting volumetry,
which is accomplished by superimposing a regular point
lattice on the tissue section and counting the points that
lie on transections of the sex cells (WEIBEL et al., 1966).
The proportion of gonadal tissue that is composed of fol-
licles containing developing or ripe gametes is reported as
Page 300
The Veliger, Vol. 26, No. 4
Figure 1
Photomicrographs of the gonadal stages of the male and female jingle shell, Anomia simplex, at 125 x magnification.
a. indifferent male or female, 18 August 1981; b. developing male, 27 May 1983; c. ripe male, 21 July 1981; d.
the “gamete volume fraction” (GVF). For any individual
bivalve, the GVF can vary between zero, for a reproduc-
tively inactive individual, and one, for an individual show-
ing maximal reproductive development. The monthly mean
GVF represents the mean of 10 estimates of the GVF
from each individual sampled. These proportions were
then arcsine transformed and the variance for each month-
ly GVF was calculated.
D. J. Brousseau, 1984 Page 301
i te ae, |
bi men tw Re
4 hs ae F :
spawning male, 24 June 1981; e. recently spent male, 10 September 1982; f. developing female, 27 May 1983; g.
ripe female, 21 July 1981; h. spawning female, 30 June 1981; i. recently spent female, 4 August 1981; j. her-
maphrodite with female phase dominant, 21 July 1981; k. hermaphrodite with male phase dominant, 25 July
1982.
RESULTS reproductive process (either spermatogenesis or oogenesis)
into distinct phases. The criteria used are based solely on
morphological observations. Categories comparable to those
The following description of the male and female de- used for other species (ROPES & STICKNEY, 1965;
velopmental stages represents an attempt to divide the BROUSSEAU, 1978, for Mya arenaria; PORTER, 1964; KECK
Categories of Gonad Condition
PERCENT
Page 302
SPENT - [_]
ripe -
SPAWNING - |IIl|
INDIFFERENT -
DEVELOPING - E&
100
80
60
40
20
Sw ’° . °°00wBB”>TV>RLxq®);h_;,Wqhw]ww
SGQqw . 9rrf
CW _,0°E?F=éwsrI] dI_))»_h)y, k})q"“"F"uh
Kot TCM A_’W
The Veliger, Vol. 26, No. 4
GZ
«_—+°}ié+ WW ’'.xw,0 yyy rm TN
KX i AAAAL0 ££
QQ QI Wow
ZK GW, rin pw>»qmqyqs9 gM
QQ Kh,.1.M
>
n
MONTHS
Figure 2
Proportions of male and female Anomia simplex with gonads in each developmental phase during 1981-1983.
et al., 1975, for Mercenaria mercenaria; BROUSSEAU, 1981,
for Petricola pholadiformis; BROUSSEAU, 1982, for Geuken-
sia demissa) were used in this study where appropriate.
Developmental Stages of the Male
Indifferent stage: The interfollicular space dominates,
consisting almost entirely of vesicular connective tissue.
The follicles are devoid of primary gonia and the absence
of gametogenic cells makes the sexes indistinguishable
(Figure 1a).
Developing stage: The spermatogenic cells begin to pro-
liferate around the follicle walls. A wide, centripetal band
of spermatogonia, spermatocytes, and spermatids devel-
ops. The interfollicular connective tissue decreases with
fewer large vacuolated fat cells being produced. The sper-
matids then differentiate into spermatozoa, which appear
as a dense mass in the lumen of the follicle (Figure 1b).
Ripe stage: The mass of mature spermatozoa increases in
volume and the individual cells arrange themselves into
bands with tails pointing toward the center of the lumen
(Figure 1c).
Partially spawned stage: There is a marked decrease in
the number of spermatozoa filling the lumen, with most
follicles empty or emptying (Figure 1d).
Spent stage: In the totally spawned male a few residual
sperm are visible but the majority of follicles are empty.
Spermatocytes are rare (Figure 1e).
Developmental Stages of the Female
Indifferent stage: The interfollicular space dominates,
consisting almost entirely of vesicular connective tissue.
The follicles are devoid of primary gonia and the absence
of gametogenic cells makes the sexes indistinguishable
(Figure 1a).
Developing stage: Oocytes become more noticeable along
the follicle walls, increasing in size and number. The de-
velopmental phase is a continuous process involving a pro-
liferation and maturation of the oocytes, with an accom-
panying reduction in interfollicular connective tissue.
Consequently, oocytes of various sizes and in various stages
of development are present in the follicle simultaneously.
The developing oocytes, which begin as hemispherical or
cylindrical cells 10-20 um in diameter and attached to the
wall of the follicle, become enlarged spherical cells as ma-
turity approaches (Figure 1f).
Ripe stage: Ripe females are characterized by the pres-
ence of large, round oocytes, 45-55 wm in diameter, some
of which are attached to the follicular wall by slender
stalks. Others appear as free oocytes in the lumen of the
follicle. There is a very prominent eccentrically placed
nucleolus visible within the nucleus (Figure 1g).
Partially spawned stage: There is a noticeable reduction
in the number of ripe oocytes present in the lumen and
some follicles are completely devoid of sex cells (Figure
1h).
D. J. Brousseau, 1984
Page 303
MEAN GVF e—e
VARIANCE e—-
GAMETE VOLUME FRACTION
500
400
<
300 >
fad
>
ra
200 O
100
JJASONDIS FMAMJJASONDIS FMAM
1981
1982 1983
MONTHS
Figure 3
Mean Gamete Volume Fraction (solid line) and variance (dotted line) for male and female Anomuia simplex.
Spent stage: Individuals that have recently undergone oo-
genesis can be recognized by the presence of a few un-
spawned oocytes in the lumen. These may be in various
degrees of cytolysis. Resumption of oogenic activity may
be evident in some individuals (Figure 11).
Reproductive Cycle
Reproductively active individuals (Developing, Ripe,
and Partially spawned) were encountered only during late
May, June, July, and August of the two years studied
(Figure 2). Gametogenesis in both sexes began in June of
1982 and in May of 1983. Fully ripe individuals were
observed in the June samples of all years studied. Spawn-
ing began almost immediately and continued through the
summer, with all of the gametes being released by August.
By September, over 90% of the A. simplex had returned
to the indifferent condition.
The “gamete volume fraction” (GVF) values for male
and female individuals from this locale are shown in Fig-
ure 3. The pattern of GVF’s and the maximum GVF
attained were similar during both years studied. The post-
spawning-reduced GVF’s occurred in the early fall. In-
creasing GVF’s due to the onset of gametogenesis were
not evident until May or June of the years studied. Peak
values of 0.87 were observed in July of both years. In
general, individuals of A. sumplex were most closely syn-
chronized (7.e., lowest variance) during fall, winter and
spring months, when, according to evidence from Figure
2, most were in an inactive condition. With the onset of
the reproductive period, the variance increased markedly,
indicating that the bivalves did not all ripen and release
gametes simultaneously. The breeding period of this species
is so abbreviated, however, that this “apparent” asyn-
chrony in spawning is in reality less dramatic in Anomia
simplex than it is in other species such as Mytilus edulis,
which spawns nearly all year (BROUSSEAU, in press).
Sex Ratios and Gonad Color
Out of the 185 individuals that could be sexed, the
proportion of females in the population (N = 87) did not
differ significantly from one-half. In nature, shell accre-
tion in Anomia simplex is extremely variable, making it
impossible to determine the size at which maturation is
reached. It appears, however, that this species matures at
a very young age since nearly all individuals sampled were
mature. Hermaphroditism was observed in four individ-
uals. From the evidence available, it appears that her-
maphroditism is simultaneous, with both spermatogenic
and oogenic cells produced in the same follicle. In half of
the hermaphrodites inspected, the female phase dominated
Page 304
The Veliger, Vol. 26, No. 4
(Figure 1}), whereas in the other half the male phase was
more pronounced (Figure 1k). Hermaphrodites were col-
lected in June, July, and August, and appeared to be
undergoing normal gametogenic development.
Gonad color in Anomia simplex varies from cream to
bright orange. Correlation between sex and gonad color,
as has been reported for Mytilus edulis (CAMPBELL, 1969;
BROUSSEAU, in press), could not be found in this species,
however. Consequently, gonad color does not serve as a
reliable indicator of sex in A. simplex.
DISCUSSION
Anomia simplex is a dioecious pelecypod, the sexes of which
are distinguishable only after examination of the gonads.
The low incidence of hermaphroditism exhibited by this
species suggests that A. simplex possesses stable gonocho-
rism, a condition characterized by the presence of some
hermaphrodites in a normally gonochoristic species. The
pattern of hermaphroditism exhibited by A. simplex is
quite unlike that found in two related families, the Os-
treidae (oysters) and the Pectinidae (scallops). In these
latter two groups, hermaphroditism is well established.
The scallops are among a group of strictly hermaphroditic
pelecypods, whereas the oysters are often cited as the best
example of hermaphroditic bivalves that undergo consec-
utive sexuality or protandry (COE, 1943b). Anomia sim-
plex, on the other hand, is rarely ambisexual and, when
such a condition is found, male and female sex cells are
produced in the same follicle rather than in separate go-
nads or separate portions of a single gonad.
Cok (1943a) describes the origin of the primary gonads
in Anomia simplex from a pair of germinal primordia lo-
cated in the posterior portion of the body. His description,
however, does not include a discussion of subsequent ga-
metogenic development in mature individuals. The evi-
dence presented here suggests that the sex cells of A. sxm-
plex ripen quickly once gametogenesis begins. In 1982
ripe gametes were produced less than one month after
gametogenesis began (Figure 2) and it seems likely that a
similar pattern would have emerged in 1983 as well. The
results of gonadal examinations indicate that Anomia sim-
plex from Woods Hole, Massachusetts, spawn annually
during the summer months. In general, North Atlantic
species of marine bivalves tend to spawn during the warm-
er months of the year (SASTRY, 1979). Nonetheless, the
reproductive period of A. semplex is considerably shorter
than that of other notable North American shallow-water
species such as Mya arenaria (ROPES & STICKNEY, 1965;
BROUSSEAU, 1978), Mercenaria mercenaria (PORTER, 1964;
KECK et al., 1975), Macoma balthica (GILBERT, 1978),
Crassostrea virginica (LOOSANOFF, 1937), Spisula solidissi-
ma (ROPES, 1968), Mulinia lateralis (CALABRESE, 1970),
Aequipecten irradians (SASTRY, 1970), Geukensia demissa
(BROUSSEAU, 1982), Petricola pholadiformis (BROUSSEAU,
1981), and Mytilus edulis (BROUSSEAU, in press). The rea-
son for this is not clear. Only after more information be-
comes available will it be possible to determine whether
the spawning pattern reported here is characteristic of this
species in all portions of its range.
LITERATURE CITED
BAYNE, B. L., D. L. HOLLAND, M. N. Moore, D. M. LOWE &
J. Wippows. 1978. Further studies on the effects of stress
in the adults on the eggs of Mytilus edulis. J. Mar. Biol.
Assoc. U.K. 58:825-841.
BRouSsSEAU, D. J. 1978. Spawning cycle, fecundity and re-
cruitment in a population of the soft-shell clam, Mya arenar-
1a from Cape Ann, Massachusetts. Fish. Bull. 76:155-166.
BROUSSEAU, D. J. 1981. Spawning cycle and fecundity in a
population of Petricola pholadiformis (Pelecypoda:Petricoli-
dae) from Milford, Connecticut. Veliger 24(1):56-61.
BROUSSEAU, D. J. 1982. Gametogenesis and spawning in a
population of Geukensia demissa (Pelecypoda: Mytilidae)
from Westport, Connecticut. Veliger 24(3):247-251.
BRoussEAU, D. J. In press. Aspects of reproduction of the blue
mussel, Mytilus edulis (Pelecypoda: Mytilidae) in Long Is-
land Sound. Fish. Bull.
CALABRESE, A. 1970. Reproductive cycle of the coot clam, Mu-
linia lateralis (Say) in Long Island Sound. Veliger 12(3):
265-269.
CAMPBELL, S.A. 1969. Seasonal cycle in the carotenoid content
in Mytilus edulis. Mar. Biol. 4:227-232.
Core, W. R. 1943a. Development of the primary gonads and
differentiation of sexuality in Teredo navalis and other pe-
lecypod molluscs. Biol. Bull. 84:178-186.
CoE, W. R. 1943b. Sexual differentiation in molluscs. I. Pe-
lecypods. Quart. Rev. Biol. 18:154-164.
GILBERT, M. A. 1978. Aspects of the reproductive cycle in
Macoma balthica (Bivalvia). Nautilus 92:21-24.
Humason, G. L. 1967. Animal tissue techniques. W. H. Free-
man Co.: San Francisco. 569 pp.
Keck, R. T., D. MAURER & H. LIND. 1975. A comparative
study of the hard clam gonad developmental cycle. Biol.
Bull. 148:243-258.
LoosanorFF, V. L. 1937. Development of the primary gonad
and sexual phases in Venus mercenaria Linnaeus. Biol. Bull.
72:389-405.
NEWELL, R.I. E., T. J. HiLBisH, R. K. KOEHN & C. J. NEWELL.
1982. Temporal variations in the reproductive cycle of
Mytilus edulis (Bivalvia, Mytilidae) from localities on the
east coast of the United States. Biol. Bull. 162:299-310.
PorTeER, H. J. 1964. Seasonal gonadal change of adult clams,
Mercenaria mercenaria (L.) in North Carolina. Proc. Natl.
Shellfish Assoc. 55:35-52.
Ropes, J. W. 1968. Reproductive cycle of the surf clam, Spz-
sula solidissima in offshore New Jersey. Biol. Bull. 135:349-
365.
Ropes, J. W. & A. P. STICKNEY. 1965. Reproductive cycle of
Mya arenaria in New England. Biol. Bull. 128:315-327.
Sastry, A. N. 1970. Reproductive physiological variation in
latitudinally separated populations of the bay scallop, Ae-
quipecten irradians Lamarck. Biol. Bull. 138:56-65.
Sastry, A. N. 1979. Pelecypoda (excluding Ostreidae). Jn: A.
C. Giese & J. S. Pearse (eds.), Reproduction of marine
invertebrates, 1:113-292. Acad. Press: New York.
WEIBEL, E. R., G. S. KISTLER & W. F. SCHERLE. 1966. Prac-
tical stereological methods for morphometric cytology. J.
Cell Biol. 30:23-38.
The Veliger 26(4):305-310 (April 2, 1984)
- THE VELIGER ©
© CMS, Inc., 1984
Influence of Varying Oxygen Tension on the
Oxygen Consumption of the Freshwater Mussel
Lamellidens marginalis (Lamarck) and Its
Relation to Body Size
V. MADAN MOHAN DAS anp S. A. T. VENKATACHARI
Department of Biosciences, Sri Krishnadevaraya University,
Anantapur (Ap) 515 003, India
Abstract. "The oxygen consumption of the freshwater mussel Lamellidens marginalis is related to the
oxygen tension of the medium. The total oxygen consumption increases, in general, with size irrespective
of oxygen tension and with oxygen tension irrespective of body size. Variations in total and unit oxygen
consumption as a function of oxygen tension are considerably less in smaller animals than in larger
animals and both decrease drastically at very low oxygen tensions. From the P. and oxygen-dependence
index values it appears that smaller animals are more independent of environmental oxygen and tend
to be regulators. Oxygen dependency increases with size, and larger animals show greater dependence
of metabolism on oxygen tension and tend to be conformers.
INTRODUCTION
THE INFLUENCE OF declining oxygen tension on oxygen
consumption has been studied in several marine and es-
tuarine bivalves, but such studies on freshwater bivalves
are relatively few. Most bivalves are supposed to be in-
dependent of oxygen tension down to a certain pressure
below which oxygen uptake falls to very low levels (VAN
Dam, 1938, 1954; GAARDER & ELLIASSEN, 1954;
ROTTHAUWE, 1958; NAGABHUSHANAM, 1962; BERG et al.,
1962; BAYNE, 1967, 1971, 1973; Moon & PRITCHARD,
1970; MANGUM & VAN WINKLE, 1973; MANGUM &
BURNETT, 1975; TAYLOR & BRAND, 1975a; BAYNE et al.,
1976; WaAITE & NEUFELD, 1977; BOOTH & MANGUM,
1978; DJANGMAH et al., 1980; Mackay & SHUMWAY,
1980). However, a few bivalves are oxygen conformers,
with their oxygen consumption decreasing with declining
oxygen tension (EDDY & CUNNINGHAM, 1934; HAmwi,
1969; BAYNE, 1971; LoMTE & NAGABHUSHANAM, 1971;
Rao et al., 1974; MANE, 1975; TAYLOR & BRAND, 1975a;
McManuon, 1979; FAMME & KOFOED, 1980; LOMTE &
JaApDuHav, 1982).
The effect of body size on the relation between oxygen
' Mailing address: Department of Zoology, Gulbarga Univer-
sity, Gulbarga, Karnataka-585 106, India.
uptake and oxygen tension has been studied in only a few
marine bivalves, and the results are inconclusive (BAYNE,
1971; TAyLor & BRAND, 1975b; FAMME, 1980; MACKAY
& SHUMWAY, 1980).
Therefore, the relation between oxygen consumption
and oxygen tension was studied in the freshwater bivalve
Lamellidens marginalis, and the probable influence of body
size on this relation was also investigated.
MATERIALS anp METHODS
The specimens collected from local streams were main-
tained in aquaria filled with water at the laboratory tem-
perature of 26-28°C for 3-4 days to allow adaptation to
laboratory conditions.
Oxygen consumption of the animals was studied using
the apparatus designed by SAROJA (1959). The apparatus
consists of a widemouthed bottle, serving as a respiratory
chamber, fitted with a four-holed rubber cork. One in-
serted tube served as the inlet and connected to the res-
ervoir, while another tube served as the outlet to collect
samples. A third tube served as the control tube for main-
taining the water level. A thermometer was fixed through
the fourth hole for monitoring temperatures. The dis-
solved-oxygen content in the water samples collected from
the apparatus before and after experimentation was de-
termined by Winkler’s iodometric method (WELSH &
Page 306
ml O2 / animal / hr
10 7X0) SO)
Soft parts wt (g)
Figure 1
Total oxygen consumption (mL O,/animal/h) in animals of dif-
ferent sizes measured at different oxygen concentrations of the
medium. Temperature ranged from 26 to 28°C. Individual points
are indicated for ‘A’ only. A, 1.13 mL/L (Po, = 29.54 mm Hg);
B, 2.83 mL/L (Po, = 72.47 mm Hg); C, 3.87 mL/L (Po, =
101.4 mm Hg); D, 4.91 mL/L (Po, = 128.6 mm Hg); E, 5.57
mL/L (Po, = 145.96 mm Hg); F, 7.56 mL/L (Po, = 197.9 mm
Hg); G, 10.20 mL/L (Po, = 267.1 mm Hg).
SMITH, 1960). From the differences in the oxygen content,
the total and unit oxygen consumptions were calculated.
Animals with soft-part weight ranging from 6-30 g
were used to cover the natural size range. Animals were
brushed thoroughly to remove algal growth over the shells
before they were introduced into the respiratory chamber.
The soft-part weight was determined at the end of exper-
iments. Oxygen consumption was determined in oxygen-
rich medium and then in media of successively decreasing
oxygen concentrations. The oxygen content of the medium
was changed by pumping either nitrogen or oxygen into
it for decreasing and increasing the oxygen content of the
medium, respectively. Experiments were carried out at the
The Veliger, Vol. 26, No. 4
ml O, /animal / hr
ml O2/g wet wt/hr
30 90 150 2lo 270
pO. (mmHg)
Figure 2
Total metabolism-oxygen tension (A) and unit metabolism-oxy-
gen tension (B) curves plotted for animals of three sizes. Broken
line indicates the oxygen tension at air saturation (26-28°C).
laboratory temperature of 26-28°C and in the afternoon
hours so as to avoid diurnal variations.
Straight lines were fitted to the data plotted on a double
logarithmic grid using the method of least squares. Other
statistical analyses were carried out using standard pro-
cedures.
RESULTS
Oxygen consumption increased with oxygen tension ir-
respective of size and also with size irrespective of oxygen
tension. However, the increase in oxygen consumption
with size was not proportional and uniform at different
oxygen tensions as indicated by the “b” values. The “b”
values decreased gradually from 0.8968 to 0.3734 as oxy-
gen content decreased from 10.2 mL/L to 2.83 mL/L.
However, the “b” value increased greatly to 1.1119 when
the oxygen content decreased further to the lowest value
of 1.132 mL/L (Figure 1, Table 1).
The increase in total metabolism and decrease in unit
metabolism as a function of body size were maintained at
V.M.M. Das & S. A. T. Venkatachari, 1984
Page 307
Table 1
Regression analysis and correlation coefficient of variations in total metabolism in relation to size in Lamellidens marginalis,
measured as a function of oxygen concentration (N = 20; level of significance = 95%).
Oxygen Reeresion Standard Correlation F aie, @
analysis 5 significance (P)
content error coefficient
(mL/L) A (log a) b of b (r) b r
A 1.13 —1.6693 1.1199 0.2229 0.8165 <0.001 <0.001
B 2.83 —0.2731 0.3734 0.1189 0.6071 <0.01 <0.001
C 3.87 —0.4206 0.5246 0.0627 0.8085 <0.001 <0.001
D 4.91 —0.4281 0.5646 0.0843 0.7784 <0.001 <0.001
E 5.57 —0.422 0.5932 0.1246 0.8074 <0.001 <0.001
F 7.56 —0.4483 0.6935 0.118 0.8264 <0.001 <0.001
G 10.20 —0.613 0.8968 0.1561 0.833 <0.001 <0.001
all levels of oxygen tension (Figure 2). Furthermore, the
variations in total and unit metabolism in relation to oxy-
gen concentration were not proportional and linear, sug-
gesting, thereby, some degree of independence of oxygen
consumption on oxygen concentration. However, these
variations were greater in larger animals and lesser in
smaller animals. Furthermore, the oxygen consumption
Kia Ks
l0g = 378 3.88
I6GOOF 209 = 807 2.84
309 1175 1.78
400
30 90
was greatly depressed when the oxygen content decreased
to the very low value of 1.32 mL/L, and this depression
was highest in smaller animals. A critical tension or oxy-
gen concentration (P,) above which there was fairly good
regulation of oxygen consumption was more prominent in
smaller animals; it was not so clear as body size increased.
It has been observed by earlier workers that P. is not
40
10 20
Soft parts wt(g)
150 2l0 270
pO2 (mm Hg)
Figure 3
The relation between oxygen tension (Po,) and the quotient of the oxygen tension and unit oxygen consumption
(Po,/Vo,) in animals of three sizes (26-28°C). Inset shows the relation between oxygen dependence index and
body size.
Page 308
necessarily a sharp point in oxygen-regulating animals;
the metabolism-oxygen curve is often hyperbolic (TANG,
1933). A more reliable estimate of oxygen dependence is
obtained by plotting Po,/Vo, against Po,. Such a plot
made for animals of three sizes showed linearity between
the two variables. The linearity was not uniform, how-
ever, and decreased with increasing size (Figure 3).
The value of K,/K, (where K, = Y intercept and K, =
slope for Po,/Vo, versus Po, plots) provides an index of
dependence of oxygen consumption on oxygen tension.
Higher ratios indicate greater dependence. A plot of K,/
K, against body size indicated that the ratio increased with
body size (Figure 3).
DISCUSSION
Aquatic animals respond to varying oxygen tension in the
surrounding medium either by regulating or conforming
their oxygen consumption. All kinds of responses of me-
tabolism to oxygen tension are found in mollusks, ranging
from total or partial dependence to complete independence
(GHIRETTI, 1966).
Though oxygen uptake in marine bivalves such as Ka-
telysia opima (MANE, 1975), Congeria salle: (RAO et al.,
1974), Mercenaria mercenaria (HAMWI, 1969), and Myt-
ilus edulis (TAYLOR & BRAND, 1975a; FAMME & KOFOED,
1980) decreases with declining oxygen tension of the me-
dium, imperfect regulation of oxygen uptake over a wide
range of oxygen tension is evident in other marine forms.
Among these imperfect regulators are Mya arenaria (VAN
Dam, 1938), Ostrea edulis (GAARDER & ELIASSEN, 1954),
Pecten grandis (VAN Dam, 1954), Martesia striata (Na-
GABHUSHANAM, 1962), Mytilus perna (BAYNE, 1967),
Mytilus californianus (MOON & PRITCHARD, 1970; BAYNE
et al., 1976), Laevicardium crassum (BAYNE, 1971), Gelo-
nia ceylonica (BAYNE, 1973), and Arctica islandica (TAYLOR
& BRAND, 1975a). Both Sphaertum simile (WAITE & NEU-
FELD, 1977) and Anadara senilis (DJANGMAH et al., 1980)
are capable of regulating their oxygen consumption within
certain limits of environmental oxygen. Rangia cuneata
(MANGUM & VAN WINKLE, 1973; MANGUM & BURNETT,
1975) is a moderate regulator, whereas in both Modiolus
demissus (BOOTH & MANGUM, 1978) and Chlamys deli-
catula (Mackay & SHUMWAY, 1980) regulatory powers
are poorly developed.
Information on the metabolic relations of freshwater
bivalves to environmental oxygen is sparse. The available
literature shows that Anodonta implicata (EDDY &
CUNNINGHAM, 1934), Parreysia corrugata (LOMTE & Na-
GABHUSHANAM, 1971), Corbicula fluminea (MCMAHON,
1979), and Corbicula regularis (LOMTE & JADHAV, 1982)
are conformers whereas good regulation of oxygen uptake
is demonstrated by Pisidium casertanum (BERG et al., 1962).
The present study shows that oxygen uptake by La-
mellidens marginals increases with the oxygen content of
the medium irrespective of body size; but this increase is
The Veliger, Vol. 26, No. 4
not proportionate and the relationship is not linear, in-
dicating that there is some degree of respiratory indepen-
dence of oxygen tension, especially in smaller animals.
However, at very low oxygen tensions, oxygen consump-
tion decreases drastically, suggesting the breakdown of
oxygen regulatory powers. A critical oxygen tension (P.),
above which there is fair regulation of oxygen consump-
tion, is perceptible in smaller individuals, but not very
clear in larger animals. The linear relationship obtained
on replotting the data, as per TANG (1933), indicates the
same. Thus, the freshwater mussel Lamellidens marginalis
is neither a strict oxygen conformer like Anodonta umpli-
cata (EDDY & CUNNINGHAM, 1934), Parreysia corrugata
(LOMTE & NAGABHUSHANAM, 1971), Corbicula fluminea
(McManHon, 1979), and Corbicula regularis (LOMTE &
JADHAV, 1982) nor a good regulator like Pisidium caser-
tanum (BERG et al., 1962). Rather, it shows some degree
of metabolic independence of oxygen tension, leading to
some regulation of oxygen consumption in relation to vari-
ations in ambient environmental oxygen.
Adequate information is not available regarding the in-
fluence of body size on the metabolism-oxygen relation-
ship. Oxygen uptake in Arctica islandica is considered oxy-
gen dependent, irrespective of body size (BAYNE, 1971);
but a more recent study (TAYLOR & BRAND, 1975b) dem-
onstrates a respiratory independence that increases with
increasing body size. Similarly, the situation is not clear
in Mytilus edulis: K,/K, values decrease with size, indi-
cating that larger individuals show less dependence on
oxygen tension than smaller individuals (BAYNE, 1971),
while K,, (oxygen dependence index) values suggest that
oxygen dependence increases with body weight (FAMME,
1980). Lesser dependence on oxygen tension with size is
also evident in Laevicardium crassum, where K,/K, also
decreases with size (BAYNE, 1971). A relation between the
oxygen dependence index and body size is also shown in
Chlamys delicatula (MACKAY & SHUMWAY, 1980).
The present study shows that the basic relation between
metabolism and size is unaltered by oxygen tension. How-
ever, “b” values for total metabolism-size curves, and the
metabolism-oxygen tension curves plotted for different size
groups, indicate a greater influence of ambient oxygen
tension on larger animals than on smaller animals. The
increase in oxygen consumption with oxygen tension is
less in smaller animals and more in larger animals. In-
terestingly, metabolism is depressed to a greater extent in
smaller animals at low oxygen tensions, and this perhaps
explains a steep increase in “‘b” value at low oxygen ten-
sion. Increased flattening of both total and unit metabo-
lism-oxygen content curves with decreases in size also il-
lustrates that oxygen uptake in smaller animals tends to
be more independent of environmental oxygen and that a
tendency toward conformity develops as body size in-
creases, though a dependable correlation between P, and
body size is not evident. However, the linearity of lines
plotted as per TANG (1933), and the increase in oxygen
V.M.M. Das & S. A. T. Venkatachari, 1984
dependence index (K,/K,) values with size, confirm that
there is some degree of respiratory independence of oxy-
gen tension and that this independence decreases with size.
The present results agree with those on Mytilus edulis
(FAMME, 1980) where respiratory independence also de-
creases with size, but they differ from those on Mytilus
edulis, Laevicardium crassum (BAYNE, 1971), and Arctica
islandica (TAYLOR & BRAND, 1975b) where respiratory
independence increases with size. It is also clear that res-
piration is nearly surface-dependent at normal environ-
mental oxygen tensions (4.91 to 7.56 mL/L), whereas it
becomes nearly weight-dependent at extreme oxygen ten-
sions (1.132 mL/L and 10.2 mL/L).
The fair degree of respiratory independence of oxygen
tension observed in Lamellidens marginalis is of ecological
significance. Low oxygen conditions are common in streams
and ponds during summer months when water levels drop
and the water becomes warmer and stagnant. In warm
surface waters, both in freshwater and in the sea, there is
much photosynthesis, and the oxygen concentration may
exceed air saturation (PROSSER, 1973). Respiratory inde-
pendence under conditions of such varying environmental
oxygen would help the animals to maintain a fairly con-
stant metabolic level. Quite interestingly, this ability seems
to be better developed in smaller animals, implying that
smaller animals can better withstand the rigors of envi-
ronmental variations.
ACKNOWLEDGMENTS
One of the authors (VMMD) is indebted to the Univer-
sity Grants Commission, New Delhi, for awarding a
Teacher Fellowship under the Faculty Improvement Pro-
gramme. Grateful thanks are due to the late Professor V.
Parvatheswara Rao, who showed keen interest in the
present study. This paper is dedicated to him.
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Physiol. 67A:171-174.
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ctenidial function related to oxygen uptake in declining oxy-
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The Veliger, Vol. 26, No. 4
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The Veliger 26(4):311-315 (April 2, 1984)
THE VELIGER
© CMS, Inc., 1984
Gaimardia bahamondei, spec. nov., from Central Chile
(Mollusca: Bivalvia: Cyamiidae: Gaimardiinae)
CECILIA OSORIO R.
Facultad de Ciencias Basicas y Farmacéuticas, Universidad de Chile,
Casilla 653, Santiago, Chile
PATRICK M. ARNAUD
Station marine d’Endoume, F-13007 Marseille, France
Abstract. The authors describe and illustrate Gaimardia bahamondei Osorio & Arnaud, spec. nov.,
from Isla Santa Maria (latitude 37°5’S; longitude 73°30’W), southeastern Pacific Ocean. Specimens
were collected on the red alga Gracilaria verrucosa found at depths of 5 m. The new species is compared
to those already known in the genus Gaimardia and its brooding habit is recorded. A new name is
proposed for G. exzlis H. & A. Adams, 1863, non Philippi, 1858: G. adamsiorum nom. nov.
INTRODUCTION
DuRING FEBRUARY 1979, the commercial exploitation of
seaweeds was hampered on the coasts of central Chile by
a small prolific bivalve growing on the red alga Gracilaria
verrucosa. The bivalve accounted for 20 and 52.3% of the
total biomass harvested during February and September,
respectively, around Isla Santa Maria.
The resulting lowering of the value of the algae drew
our attention to this bivalve that we have identified as a
new representative of the genus Gaimardia Gould, 1852,
a genus characteristic of the southern oceans (ARNAUD,
1974). This bivalve is here described as Gaimardia (Gai-
mardia) bahamondei Osorio & Arnaud, spec. nov.
Bivalvia Linné, 1758
Cyamiacea Philippi, 1845
Cyamiidae Philippi, 1845
Gaimardia Gould, 1852
Gaimardia (Gaimardia) bahamondei
Osorio & Arnaud, spec. nov.
(Figures 1 to 5)
Description—shell morphology: Shell small (maximum
length 7.7 mm), sub-ovate to sub-trapezoidal (Figures 1,
2), convex, thin, delicate, equivalve, and inequilateral.
Beaks prosogyrate, prominent, anteriorly placed, and ad-
jacent. Periostracum salmon red, some individuals lighter
red to white.
Anterior margin slanting, merging smoothly into the
ventral margin through a blunt rostrum. Posterior margin
uniformly rounded. Dorsal margin nearly straight. Ven-
tral edge almost straight, sometimes with slight undula-
tion at the point where byssus emerges. Without byssal
gap, or with very narrow one.
Outer surface smooth, with tenuous and regular micro-
scopic growth lines.
Hinge plate narrow. Two cardinal teeth on the right
valve: the dorsal tooth triangular (Figure 3B) and the
ventral tooth cylindrical and projecting (Figure 3A). Left
valve with one cardinal tooth, elongated, wavy, anterior
end rounded, fitting between teeth on right valve. Liga-
ment dorsal, partially sunken, long, narrow, beginning
behind the umbo (Figure 3).
Inner surface smooth, with faint muscle scars. Adductor
scars slightly unequal: the anterior scar elongate, sub-
oval, tapering to a pointed upper tip; the posterior scar
less elongate and rounded. Anterior retractor muscle scar
small, located close to upper edge of anterior adductor
scar; posterior retractor scar coalesced with posterior ad-
ductor (Figure 4).
Description—anatomy: Mantle thin, transparent, smooth,
and thickened at the edges which are joined by a mem-
brane leaving three openings: anterior or pedal opening
Page 312
1 mm
Figure 1
Gaimardia bahamondei Osorio & Arnaud, spec. nov.
medium sized; median or branchial opening almost twice
as long as pedal opening; and posterior or anal opening
about half as long as pedal opening (Figure 4). Sutures
between these three openings are subequal in length.
Gills large, unequal, developed on both sides. Outer
demibranch, elongate dorso-ventrally, and having a point-
ed posterior tip (Figure 4). Inner demibranch sub-quad-
rangular, nearly twice the size of the outer. Demibranchs
joined posteriorly, anterior edges free. Both demibranchs
are used for incubation of the eggs and juveniles.
Foot moderately developed, linguiform, directed ante-
riorly (Figure 4). The byssal gland is open at its posterior
part, the byssus being formed by few very thin, translucent
white fibers.
The anatomy of Gaimardia was studied or discussed,
mostly in G. trapesina (under various names), by J. E.
Gray (1854), M. E. Gray (1857), PELSENEER (1903),
IGEL (1908a, b), ODHNER (1924), and PONDER (1971).
The anatomy of the new species is in general agreement
with that previously described in these other representa-
tives of the genus.
Type locality: Chile, Isla Santa Maria (37°5'S; 73°30’W)
in the Golfo de Arauco, near Concepcion, 4.5 to 5 m deep,
on the red alga Gracilaria verrucosa (Hudson), March 1979.
Type material: Holotype—6.7 mm long x 5.0 mm high.
Museo Nacional de Historia Natural, Santiago de Chile.
No. ML 100244.
Paratypes—12 specimens 2.6-6.0 mm long, Museo
Nacional de Historia Natural, Santiago de Chile, No.
ML 100235. Other paratypes are deposited in Museum
National d’Histoire Naturelle, Paris, France; U.S. Na-
tional Museum, Washington, U.S.A.; Los Angeles Coun-
ty Museum, U.S.A.; and British Museum (Natural His-
tory), London, U.K.
The Veliger, Vol. 26, No. 4
D
E
1mm 1mm
= a —____I
Figure 2
Variation of the outline of Gaimardia bahamondei, from sub-
oval (D) to sub-trapezoidal (E), during its growth.
Etymology: This new species is kindly dedicated to Pro-
fessor Nibaldo Bahamonde, investigator at the Museo Na-
cional de Historia Natural and Professor at the Univer-
sidad de Chile, in recognition of his work.
Biological notes: The size of specimens we have exam-
ined varies from 1.3 mm long X 1.1 mm high to 7.7 mm
long X 6.0 mm high. The specimens tend to become trap-
ezoidal in outline as their size increases (Figure 2). The
size structure of the population (Figure 5) indicates the
presence of juveniles (less than 4 mm in length) and adults
between 4 and 7 mm long; adults account for about 75
per cent of the population.
Individuals are reproductive from 4 to 7 mm in length.
In the inner demibranchs, we counted as many as 949
broods in a single female 7 mm long. The size of broods
varies between 130 and 430 um. A similar brooding habit
is well known in the Macrocystis-associated G. trapesina.
Status of the subfamily Gaimardiinae: The genus Gar-
mardia was formerly considered as part of the family Gai-
mardiidae among the superfamily Gaimardiacea (see
FLEMING, 1969). PONDER (1971) has shown that it is
preferable to regard this family as a subfamily in the
Cyamiidae of the superfamily Cyamiacea. This proposal
has been recently questioned by MORTON (1979), but we
accept it until more evidence is available.
Among the genus Gaimardia, three subgenera may be
distinguished: the primitive subgenera Neogaimardia
Odhner, 1924 (see Morton, 1979) and Progaimardia
Ponder, 1971, and the more evolved subgenus Gaimardia
(s.s.).
Comparisons of G. bahamondei with other species: Our
material from Isla Santa Maria was compared to the var-
ious representatives of the genus Gazmardia and related
genera. This was done on the basis of examination of type
material preserved in the Museum National d’Histoire
Naturelle, Paris (types of Rochebrune and Mabille) and
in the British Museum (Natural History), London (types
C. Osorio R. & P. M. Arnaud, 1984
Page 313
Figure 3
Gaimardia bahamondei Osorio & Arnaud, spec. nov., hinge region of both valves. Right valve: A, dorsal cardinal
tooth; B, ventral cardinal tooth; L, ligament. Left valve: C, cardinal tooth; L, ligament.
of H. & A. Adams and Preston); we compared these types
to recent samples from Kerguelen and Crozet Islands. It
is obvious that the species from central Chile does not
belong to the primitive subgenera Neogaimardia Odhner,
1924 (see MorTON, 1979) or Progaimardia Ponder, 1971,
both having well developed hinges. Ga:zmardia bahamon-
dei Osorio & Arnaud, spec. nov., is a member of the
subgenus Gaimardia (s.s.) and more-or-less intermediary
in all its characteristics between Gaimardia (Gaimardia)
exilis (H. & A. Adams, 1863) and the much more-evolved
Gaimardia (G.) trapesina (Lamarck, 1819).
Coincidentally we must rename this Gaimardia exilis
(H. & A. Adams, 1863): another species, Phaseolicama
exilis Philippi, 1858, has to be accepted into the genus
Gaimardia (because Phaseolicama Rousseau, 1854, is a ju-
nior synonym of Gazmardia Gould, 1852: see, for example,
FLEMING, 1969). So we propose to rename Gaimardia ex-
iis H. & A. Adams non Philippi: Ga:mardia adamsiorum,
nom. nov.
The species from central Chile may be distinguished
from Gaimardia adamsiorum, nom. nov. (redescribed and
figured by SMITH, 1877, and PONDER, 1971, and available
to us from the Falkland Islands as type material, and from
the Kerguelen Islands) by several characters: G. baha-
mondei has a blunt rostrum, a thin shell, comparatively
small cardinal teeth (however, they become more and more
indistinct with age in G. adamsiorum), and lacks lateral
teeth.
Gaimardia trapesina is a variable species that has re-
ceived many names (see, for example, DELL, 1964), in-
cluding the following based on material from southern
South America or South Georgia Island: Phaseolicama ma-
gellanica Rousseau, 1854; Modiolarca nigromarginata, M.
subquadrata and M. faba Pfeffer, in Martens & Pfeffer,
1886; and M. crassa, M. lecannelierr, M. lephayi, M. sa-
vatiert, M. fuegiensis, M. sauvineti and M. hahni Roche-
brune & Mabille, 1889. But the new species differs from
G. trapesina by the following characters: a poorly-marked
rostrum (always well-developed in G. trapesina), the car-
dinal teeth (very inconspicuous in G. trapesina), and the
relative length of the three mantle openings. In G. trape-
sina the two ventral openings are subequal and separated
by a suture longer than either; the anal opening is smaller
(half the length of the other two openings). Other less
diagnostic characters are the size of the foot (less devel-
oped in G. bahamondei), the color of the shell (salmon
red as opposed to yellowish, brown or purplish brown in
G. trapesina), and the habitat (G. trapesina being epibiotic
on the large kelp Macrocystis pyrifera).
Gaimardia exilis Philippi was described without illus-
tration, and we failed to trace the type material. At this
stage, its true nature must be questioned, but according
Page 314
The Veliger, Vol. 26, No. 4
mo
Figure 4
Gaimardia bahamondei Osorio & Arnaud, spec. nov., with left valve removed. aas, anterior adductor scar; ao,
anterior (or pedal) opening; ars, anterior retractor scar; b, beak; f, foot; g, gonad; idb, gill inner demibranch; L,
ligament; mo, median (or branchial) opening; odb, gill outer demibranch; pas, posterior adductor scar; po, posterior
(or anal) opening; prs, posterior retractor scar.
to the description, this is neither G. adamsiorum nom. nov.,
nor G. bahamondei spec. nov.
Other related species, originally described in the genus
Modtolarca, are G. mesembrina (Melvill & Standen, 1907)
20
15
r !
5
Number (%)
Ny 2 Su 4S Sn On laity
Length (mm)
Figure 5
Gaimardia bahamondei Osorio & Arnaud, spec. nov. Population
structure according to size (arrow indicates minimum size at
maturity).
and its synonym M. picturata Cooper & Preston, 1910;
M. gemma Cooper & Preston, 1910; and M. bennett: Pres-
ton, 1913. The taxonomic status of these species is un-
clear; there are probably some other synonyms among
them, and some will probably have to be referred to Kid-
deria Dall, 1886 (in the subfamily Cyamiinae of the fam-
ily Cyamiidae sensu PONDER, 1971) instead of Gazmardia.
We disagree with BERNARD (1983) who lists the first three
names as additional synonyms of G. trapesina. In any event,
we consider that the elongate shape, the color, and the
hinges (when they are known) distinguish these species
sufficiently from our Chilean material.
Finally, G. kerguelensis (Smith, 1885), known only from
the type locality (Kerguelen Islands, south Indian Ocean),
also has a very different elongate shape, and other char-
acters showing no close affinities with the material from
Isla Santa Maria.
ACKNOWLEDGMENTS
For the loan of type material we thank Drs. P. Bouchet
and B. Métivier from the Museum National d’Histoire
Naturelle, and Dr. J. B. Taylor and Mrs. S. Morris from
the British Museum (Natural History). We also thank
C. Osorio R. & P. M. Arnaud, 1984
Miss M. E. Lagos, Mr. U. Ohme, and S. Santa Cruz who
donated specimens.
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SMITH, E. A. 1877. Mollusca. Jn: An account of the petrologi-
cal, botanical and zoological collections made in Kerguelen’s
land and Rodriguez during the Transit of Venus Expedi-
tion. Trans. Roy. Soc. Lond., Extra Vol. 168:167-192,
jell, &.
SMITH, E. A. 1885. Report on the Lamellibranchiata collected
by H.M.S. Challenger during the years 1873-1876. Rep.
Sci. Res. Voy. H.M.S. Challenger 13:1-341, plts. 1-23.
The Veliger 26(4):316-319 (April 2, 1984)
THE VELIGER
© CMS, Inc., 1984
Egg Masses and Larvae of Three Species of Cerithium
from the Arabian Sea
by
SOHAIL BARKATI anpD MUZAMMIL AHMED
Institute of Marine Biology, University of Karachi, Karachi-32, Pakistan
Abstract.
An illustrated account of breeding habits and early larval development of three species of
Cerithtum from the coast of Karachi, northern Arabian Sea is given for the first time. Cerzthium morus
was studied earlier from tropical waters; however, the habits and development of the other two species,
C. sinensis and Cerithium sp., are described here for the first time. Cerithium morus and C. sinensis
deposit egg strings from which veligers hatch, whereas Cerithium sp. is ovoviviparous.
INTRODUCTION
THE BREEDING HABITS and larval development of gastro-
pods of the genus Cerithium have only occasionally been
studied. This work has been done on species found in the
north Atlantic and Pacific Oceans by the following work-
ers: LEBOUR, 1945; OSTERGAARD, 1950; FRETTER & GRA-
HAM, 1962; DAvis, 1967; WOLFSON, 1969; D’Asaro, 1970;
Houprick, 1971, 1973; and CANNON, 1975. NATARAJAN
(1957) has described the egg masses of C. morus from the
Indian Ocean, and Lo BIANCO (1888, in Housrick, 1973)
studied the egg mass of C. vulgatum from the Mediterra-
nean Sea. Members of the family Cerithiidae are fairly
abundant on the rocky beaches near Karachi, Pakistan.
The present paper describes the breeding habits and early
larval development of three species of Cerithium from this
coast.
MATERIALS ann METHODS
Specimens of three species of Cerzthium were collected
from the rocky beaches at Manora and Buleji (see BAR-
KATI & AHMED, 1983, for ecological notes on these beach-
es) in the Karachi area. Collections were made at regular
biweekly intervals from July 1976 to June 1977. After
each collection, specimens were placed for spawning in
1600-mL finger bowls in which water was changed daily
and aerated continuously. The temperature of seawater
in the bowls in the laboratory ranged from 28 to 31°C.
All three species spawned to one extent or another in the
laboratory. A microscopic study was also made of the lar-
vae and juveniles that hatched from the egg masses or from
individuals. Dimensions of the shells of the developing
larvae were measured with an oculomicrometer, and il-
lustrations were prepared with a camera lucida.
OBSERVATIONS
Breeding Season
Cerithium sinensis occurs fairly commonly on the rocky
coast at Buleji (near Karachi) near the low-water mark,
at a tidal height of about +0.15 to 0.3 m; at this level the
snails are exposed only at very low tides. In the labora-
tory, specimens of this species deposited egg masses on the
following dates: June 20, July 3, October 26, 29 and 31,
November 1 and 11 in 1976, and July 25, 1977. In ad-
dition, two egg masses of this species were collected from
the rocky beach at Paradise Point and Buleji on December
7 and 20, 1976.
Cerithium morus occurs on the same rocky beach (at
Buleji) as C. sinensis but higher up at a tidal height of
about 0.9 to 1.5 m. It is one of the most abundant species
of gastropods on the open rocky coast of Karachi. Speci-
mens of this species deposited egg masses in the laboratory
on the following dates during the year 1976: June 7, Sep-
tember 4, October 19, 22, 30, and 31, and November 1.
Altogether, 10 specimens which had been collected from
Buleji and Manora spawned in the laboratory.
Cerithium sp. also occurs in the mid-tidal zone of the
rocky beaches at Manora and Buleji, but it is less abun-
dant than C. sinensis and C. morus. This species remains
unidentified so far; however, voucher specimens of this
species have been retained at the Institute of Marine Bi-
ology, University of Karachi, for future studies. In the
laboratory, Cerithium sp. liberated a few juveniles on Oc-
tober 14.
No spawning occurred in months, other than those in-
dicated, although specimens of all three species were ex-
amined for spawning throughout the year.
S. Barkati & M. Ahmed, 1984
Figure 1
Cerithium sinensis: A. top view of an egg mass; B. portion of an
egg mass enlarged; C. ventral view of newly hatched larval shell;
D. ventral view of 24-h veliger shell; E. dorsal view of 48-h
larval shell.
Egg Masses
Cerithium sinensis: The spawn of C. sinensis is described
here for the first time. However, NATARAJAN (1957) ear-
lier reported the spawn of an unidentified species of Cer-
ithium from the Gulf of Manaar (India) that closely re-
sembles the present egg mass.
Table 1
Dimensions of eggs and larval shells of Cerithium sinensis
and C. morus at various stages of development. The values
in the table are means + 1 standard deviation, followed
by the number of observations in parentheses.
Cerithium morus
99 + 5.49 (16)
3-4 +0.55 (5)
Cerithium sinensis
94 + 6.75 (19)
4-5 + 0.49 (7)
Egg diameter (um)
Incubation period
(days)
No. eggs/mass 5438 10,490
Larval shell height 160 + 10.5(25) 132 + 8.45 (18)
at hatching (um)
Larval shell width 12) se 53 (M5) 1313} ae GIO) (Gls)
at hatching (um)
Larval shell height 187 + 4.99 (18) 176 + 5.47 (16)
after 48 h (um)
Larval shell width
after 48 h (um)
149 + 5.93 (18) 145 + 11.11 (16)
Larval shell height — 246 + 13.03 (5)
after 13 days (um)
Larval shell width — PS) se O55 (©)
after 13 days (um)
05mm
SS,
Figure 2
Cerithium morus: A. top view of an egg mass; B. portion of an
egg mass enlarged; C and D. dorsal and ventral views of larval
shells just after hatching; E and F. dorsal and ventral views of
48-h larval shells.
Deposition of egg masses of C. sznensis occurred at night.
In the morning, laying of the egg masses was found to
have been completed, indicating that these were deposited
without interruption. They were usually deposited on the
bottom of the containers. The two egg masses that were
obtained from the field were collected from the sandy layer
covering the surface of rocks.
The spawn of C. sinensis (Figure 1A) consisted of loose-
ly coiled, or straight, long thin white tube-like strings.
The strings measured on an average 1 mm wide and 67
mm long (SD = 15.28, N = 5). Free-swimming veligers
hatched from these egg masses 4-5 days after their de-
position. Dimensions of eggs and larvae at various stages
of development are given in Table 1. At hatching the outer
lip of the larval shell was extended in the middle and
became more pronounced as the shell grew.
Cerithium morus: The spawn of C. morus was earlier de-
scribed by NATARAJAN (1957) from the Gulf of Manaar
(India).
In the present study the egg masses of C. morus were
found to be deposited at night on the side walls of the
glass bowls and only occasionally (in one out of ten cases)
on the bottom. At spawning, the egg masses consisted of
a narrow transparent, colorless, gelatinous tube, 0.5 mm
wide and 92-196 mm long (SD = 35.22, N = 7), forming
several coils compactly arranged and touching each other
at several points. In one case the spawned mass covered
Page 318
100U
——
Figure 3
Cerithium sp. A. Larval shell 24 h after hatching; B. larval shell
96 h after hatching.
an area 25-36 mm long and 5-7 mm wide. The eggs were
contained in egg capsules which were embedded in the
gelatinous material of the egg mass. The eggs were more-
or-less spherical, and so were the individual egg capsules
(Figure 2B).
Larvae hatched from the capsules as free-swimming
veligers (Figure 2C). At room temperature, which ranged
from 28 to 31.5°C with an average of 30.2°C (SD = 0.92),
the incubation period was 3-4 days but extended to 8 days
in some cases. At hatching the larvae possessed transpar-
ent sculptureless shells. Subsequently, their outer lips
formed a beaklike structure and developed a few stria-
tions; the umbilicus became more distinct. They survived
in the laboratory for 15 days without food. At this stage
their shells became thick and vertical striations became
prominent.
Cerithium sp.: Five miniature snails of this species were
found swimming actively in the finger bowls on the morn-
ing of October 14, 1976. The bowls were searched care-
fully for egg capsules, but none were found. Evidently,
these juveniles had been extruded at night by the speci-
mens placed for spawning. This species, therefore, seems
to be ovoviviparous and its larvae seem to have direct
development. The juveniles resembled the adults in the
shape of their shells, which in both had a projected and
recurved siphonal canal. The juvenile shells had translu-
cent thick walls and were composed of two and a half
whorls (Figure 3A). They survived in the laboratory for
four days without food, and measured 798 um high and
599 um wide (Figure 3B). They were preserved alive after
four days for future study. By this time, axial ribs started
appearing on the projected siphonal canal.
DISCUSSION
Cerithium sinensis and C. morus spawn on the coast of
Karachi during the monsoon and postmonsoon season from
June to December. The single instance of spawning ob-
served in the unidentified species of Cerithium from Ka-
The Veliger, Vol. 26, No. 4
rachi (in October) indicates that it also spawned during
the postmonsoon season. On this coast the gastropod Plan-
axis sulcatus was found to breed from January to August
(BaRKATI & AHMED, 1982) and four species of Thais in
spring and summer (BARKATI & AHMED, 1983). AHMED
(1980) has categorized the marine organisms of the coast
of Pakistan from the standpoint of their spawning seasons,
as monsoon, winter-spring, spring-summer, and year-
round spawners. The three species of Cerithium do not
seem to fit this scheme. Knowledge of the spawning of
these species, however, is based mostly on the deposition
of egg masses in the laboratory, and may not truly reflect
the situation prevailing in the field. The spawning season
of C. sinensis, which occurs very low in the intertidal zone,
might be expected to extend to the winter and spring
months, or even throughout the year. This would conform
with the conclusion, drawn by AHMED in his recent review
(1980), that marine organisms of the coast of Pakistan (a
subtropical coast) that occur close to the low tide mark or
subtidally have a tendency to spawn in the winter and
spring months and in some cases throughout the year.
The nature of the larval development of the three species
needs further consideration. It is known that indirect de-
velopment is the usual method of reproduction in members
of the genus Cerzthium compared to direct development,
which has so far been reported from only two species,
namely C. muscarum and C. variabile (HOUBRICK, 1973).
The three species of Cerithium reported herein can be
placed in two groups according to their mode of devel-
opment. In the first type, the egg mass consists of filaments
containing egg capsules from which free-swimming larvae
hatch, as in C. senensis and C. morus. The second type is
represented by Cerithium sp. in which miniature snails
hatch directly from the parent. In this case, juvenile snails
settled on the bottom after only a brief period of swim-
ming. Although this is the first time a species of Cerithium
has been found to possess viviparous development, this
mode of development is not new to the present environ-
ment: another prosobranch, Planaxis sulcatus, has recently
been shown to be viviparous. Thus, the observations made
during the present study show that, in addition to the
usual method in which gelatinous filaments containing egg
capsules are produced, extrusion of juveniles from the
mother snails may also occur.
The number of eggs per spawn has been described ear-
lier for a number of species of Cerzthium (see HOUBRICK,
1973). This ranges from 8800 in C. literatum to 90,000
in C. auricoma. The spawns of C. morus and C. sinensis
were found in the present study to contain an average of
10,490 and 5438 eggs, respectively. The number of eggs
per spawn in C. sinensis, therefore, is the lowest of all the
Cerithium species studied so far.
LITERATURE CITED
AHMED, M. 1980. The breeding and recruitment of marine
animals of the coast of Pakistan bordering the Arabian Sea.
Proc. First Pakistan Cong. Zool., pp. 55-96.
S. Barkati & M. Ahmed, 1984
BaRKATI, S. & M. AHMED. 1982. Studies on the reproductive
biology of some prosobranchs from the coast of Karachi
(Pakistan) bordering the northern Arabian Sea. I. Obser-
vations on Planaxis sulcatus (Born, 1780). Veliger 24(4):
355-358.
BARKATI, S. & M. AHMED. 1983. Studies on the reproductive
biology of some prosobranchs from the coast of Pakistan
bordering the northern Arabian Sea. II. Egg capsules and
larvae of four species of Thais. Veliger 26(1):30-36.
Cannon, L. R. G. 1975. On the reproductive biology of Cer-
ithium moniliferum at Heron Island, Great Barrier Reef.
Pac. Sci. 4:353-359.
D’Asaro, C. N. 1970. Egg capsules of prosobranch mollusks
from South Florida and the Bahamas with notes on spawn-
ing in the laboratory. Bull. Mar. Sci. 20:414-440.
Davis, C. C. 1967. Emergence of veliger larvae from eggs in
gelatinous masses laid by some Jamaican marine gastro-
pods. Malacologia 5:299-309.
Page 319
FRETTER, V. & A. GRAHAM. 1962. British prosobranch mol-
lusks. Ray Society: London. 755 pp.
Houprick, J. R. 1971. Some aspects of the anatomy, repro-
duction, and early development of Cerithium nodulosum
(Bruguiere) (Gastropoda:Prosobranchia). Pac. Sci. 25:560-
565.
Housrick, J. R. 1973. Studies on the reproductive biology of
the genus Cerithium (Gastropoda:Prosobranchia) in the
western Atlantic. Bull. Mar. Sci. 23:875-904.
Lepour, M. V. 1945. The eggs and larvae of some proso-
branchs from Bermuda. Proc. Zool. Soc. Lond. 114:462-
489.
NATARAJAN, A. V. 1957. Studies on the egg masses and larval
development of some prosobranchs from the Gulf of Manaar
and the Palk Bay. Proc. Indian Acad. Sci. B. 46:170-228.
OSTERGAARD, J. M. 1950. Spawning and development of some
Hawaiian marine gastropods. Pac. Sci. 4:75-115.
Wo tFson, H. 1969. Spawning notes. IV. Cerithium stercus-
muscarum. Veliger 11(4):441-442.
The Veliger 26(4):320-326 (April 2, 1984)
THE VELIGER
© CMS, Inc., 1984
Male Reproductive System of Chorus giganteus
(Lesson, 1829) (Muricidae: Prosobranchia):
Anatomical and Histological Description
by
MARTA AMIN V., IRENE LEPEZ G., OSCAR MARIN S. anp MAYA DELPIN A.
Facultad de Ciencias Biologicas y de Recursos Naturales,
Universidad de Concepcion, Concepcion, Chile
Abstract. The male reproductive system of Chorus giganteus is anatomically and histologically de-
scribed. This system is formed by a testis, seminal vesicle, posterior deferent duct, prostate, anterior
deferent duct, and penis. Besides the germ cells, the occurrence of some large cells inside the seminiferous
tubules is reported; these cells may play a role similar to that of nurse cells. Also, polynucleated cellular
masses are observed corresponding to gonia with incomplete cytokinesis. At the posterior end of the
prostate, the lumen of the gland is connected with the mantle cavity by means of a duct, which, toward
the anterior zones, is replaced by a double sheet of epithelium-like cells corresponding to the so-called
line of fusion of the open system from less-advanced forms. The line of fusion extends from the duct,
connecting with the mantle cavity at the posterior limit of the prostate, along the entire length of the
male duct to the penis.
INTRODUCTION
THE FAMILY MUuRICIDAE has a wide geographical distri-
bution. Previous studies have revealed the existence of
similarities in the anatomical and histological organiza-
tion of the reproductive system not only among the species
of this family (FRETTER & GRAHAM, 1962, in WEST, 1979;
PURCHON, 1977; HYMAN, 1967), but also among those of
the neogastropod families Buccinidae (WEsT, 1979), Col-
umbellidae (HOUSTON, 1976), and others.
Chorus giganteus (Lesson, 1829) is a muricid living on
sandy and muddy sea bottoms, 8-30 m deep (LEPEZ, 1981).
Its geographical distribution extends from Antofagasta
(23°40’S; 70°25'W) through Valdivia (39°55’S; 73°10'W),
Chile (Osorio, 1979).
Since Chorus giganteus is an edible snail that has re-
cently acquired economical importance, studies on differ-
ent aspects of the reproductive biology have been initiated.
In the last two years, studies have been done on the re-
productive cycle (LEPEZ, 1981), the intracapsular devel-
opment of eggs and larvae (GALLARDO, 1981), and fecun-
dity (OLAVE, 1981) of this species. In the present paper
an anatomo-histological study of the male reproductive
system is reported.
MATERIALS anp METHODS
Sexually mature individuals were collected at Burca
(36°28'S; 75°55'W), Concepcion, Chile, by scuba diving
and maintained in running seawater aquaria at the Ma-
rine Biology Station of the University of Concepcion. An-
atomical descriptions were made from live specimens and
10% formalin-fixed material.
For the histological study, tissues were excised from
freshly dissected animals and fixed for a minimum of 24
h in 10% formalin. Following fixation, tissues were de-
hydrated through a graded series of ethanol and embedded
in paraffin (Merck 56-58°C).
Serial sections 5-6 wm thick were cut and mounted on
albuminized slides.
The following stains were used: (1) Hematoxylin-
Phloxine (HUMASON, 1967), (2) Heidenhain’s azan
(HuMaSON, 1967), (3) PAS with amylase control (LILLIE,
1965), (4) Feulgen reaction (LILLIE, 1965), and (5) Meth-
yl Green-Pyronine (LILLIE, 1965).
RESULTS
Anatomy
The male reproductive system of Chorus giganteus is
formed by a single testis, seminal vesicle, posterior defer-
ent duct, prostate, anterior deferent duct, and penis (Fig-
ures 1, 2).
Testis
The testis (Figures 1, 2) of a sexually mature male is
a single mass located in the last whorls of the shell. The
M. Amin V. et al., 1984
TE
Figure 1
Male Chorus giganteus. Whole specimen with shell removed. TE,
testis; PR, prostate; ADD, anterior deferent duct; PE, penis.
testis adheres to the dorsal side of the digestive gland along
its total length. No clear separation is observed with re-
spect to the digestive gland because the efferent ductuli of
the testis slightly intrude between the tubules of the glan-
dular mass. The testis color varies from dark brown to
light yellow depending on the stage of gonad development.
The efferent ductuli join to form a single spermatic duct
(Figure 2) that leaves the testis and then passes superfi-
cially along the columellar side of the visceral mass.
Seminal vesicle
After leaving the testis, the spermatic duct becomes con-
voluted constituting a seminal vesicle (Figure 2), which
measures 3-4 mm in length. The seminal vesicle is filled
with spermatozoa.
Posterior deferent duct
Following the seminal vesicle, the spermatic duct (Fig-
ure 2), which lies laterally to the visceral mass in the inner
side of the whorls, straightens and passes between the
heart and kidney.
PDD
TE
Page 321
Prostate
The posterior deferent duct extends into the prostate
(Figure 2), which is located along the right side of the
roof of the mantle cavity (Figures 1, 2). The prostate,
which encloses the spermatic duct, is a glandular mass
about 30 mm long, depending on the developmental stage
of the specimen.
Anterior deferent duct
After leaving the prostate, the spermatic duct, referred
to as the anterior deferent duct (Figure 2), goes straight
down to the floor of the mantle cavity. Once on the floor
of the mantle cavity, the duct extends a small distance
along the mantle cavity laterally, following the curvature
of the cavity, and then running anteriorly to the penis
along the body wall. The course of the anterior deferent
duct runs mainly on the surface of the floor of the mantle
cavity (Figure 1).
Penis
This organ is compact, with a wide base and a fusiform
distal end (Figures 1, 2). It is dorso-ventrally flattened
and situated behind and at the right side of the tentacles.
Average length is about 20 mm.
Histology
Testis
The testis, together with the digestive gland, is covered
by the pallial epithelium, which is a simple cuboidal type.
The cells of the epithelium have round basal nuclei. Sub-
jacent to the pallial epithelium is a thin albuginea.
The testis is composed of many convoluted seminiferous
tubules with an average diameter of 130 um (Figure 3).
Each tubule is externally delimited by a thin adventitium.
The germinal epithelium underlying the external adven-
titia is composed of spermatogenic cells clustered in groups;
all cells in a group are in the same maturation phase.
ADD
PE
Figure 2
Male reproductive system. TE, testis; SV, seminal vesicle; PDD, posterior deferent duct; OMC, opening to the
mantle cavity; PR, prostate; ADD, anterior deferent duct; PE, penis.
Page 322 The Veliger, Vol. 26, No. 4
M. Amin V. ef al., 1984
Among the basal germ cells, and resting on the adventitia,
there are a few larger cells each with a less densely stain-
ing nucleus; no nitid cell limits are observed.
Germ cells
(a) Spermatogonia: These are round cells with a large ho-
mogeneous, deeply staining nucleus, and scanty cy-
toplasm. They lie adjacent to the basal lamina on the
luminal side of the germinal epithelium.
(b) Primary spermatocytes: Spermatocytes and spermato-
gonia are of the same size, but the nucleus of the
former is more delimited and laterally located, with
groups of meiotic chromosomes. Secondary spermato-
cytes are indistinguishable from primary spermato-
cytes.
(c) Spermatids: Early spermatids are small, rounded cells
with a central, spherical, homogeneous nucleus and
scanty cytoplasm. The morphology of these cells var-
ies during spermiogenesis and they tend to be elon-
gate.
(d) Spermatozoa: These are slender fusiform cells with a
total length of 98.75 um. The head, 57.19 um long, is
pointed and slightly wider than the tail.
The seminiferous tubules occasionally contain polynu-
cleated masses corresponding to gonias with incomplete
cytokinesis (Figure 4).
Seminal vesicle
The convoluted portion of the spermatic duct, the sem-
inal vesicle, is lined with a simple cuboidal ciliated epi-
thelium. The epithelial cells contain a lightly staining cy-
toplasm, a large oval central nucleus, and very long cilia
(30 wm). Beneath the epithelium and between the loops
of the duct, dense connective tissue and free blood cells
are seen. At the distal end, the seminal vesicle has a
sphincter with abundant muscle fibres interspersed with
the connective tissue surrounding the epithelium.
Posterior deferent duct
The posterior deferent duct is internally lined with a
simple cuboidal ciliated epithelium resembling that of the
seminal vesicles, but in this portion of the spermatic duct
the epithelium greatly invaginates and no spermatozoa are
Page 323
seen in the lumen. Beneath the epithelium a thin PAS-
positive line is observed. The cuboidal epithelium is ex-
ternally surrounded by dense connective tissue with a few
intermingled muscle fibres and spaces with blood cells.
Prostate
The prostate is a glandular differentiation of the wall
of the deferent duct which greatly evaginates toward the
lumen (Figure 5). The gland is delimited internally by a
simple ciliated columnar epithelium, although in some
zones the epithelial cells increase in height and intrude
into the underlying glandular mass. The cytoplasm of the
epithelial cells contains fine granules which stain with
Phloxine, and larger PAS-positive granules. The nuclei
of the epithelial cells are located in a basal position and
their shape varies from spherical to fusiform. The cilia
are shorter (14-15 wm) than those of the posterior deferent
duct. Goblet cells intermingle with the epithelial cells.
Underlying the epithelium is the glandular tissue, which
is composed of a mass of secretory cells arranged in ra-
dially branched tubules converging towards the prostate
lumen. The secretory tubules are separated by thin septa
of connective tissue. The glandular cells close to the cil-
iated epithelium show a great amount of secretory mate-
rial gradually decreasing toward the outer limit of the
prostate. In this area the cytoplasm of the secretory cells
is dominated by large vacuoles displacing the nucleus to
the periphery of the cell. The nucleus is large and spher-
ical, and contains granular and loose chromatin.
Externally surrounding the glandular zone, loose con-
nective tissue with fibres concentrically arranged around
the prostate is observed.
At the posterior end of the prostate, the lumen of the
gland is connected with the pallial cavity by a small duct
(Figure 6). This duct is about 124 wm in diameter and
1.116 mm in length. It is lined with a pseudo-stratified
ciliated columnar epithelium containing fusiform nuclei.
The goblet cells of the epithelium are filled with granules
that stain deeply with Phloxine.
In serial sections toward the anterior end of the pros-
tate, the duct connecting the lumen and the pallial cavity
no longer is observed; instead, a double sheet of epithe-
lium-like cells runs all the way along the gland. This
double sheet of epithelium-like cells is immersed in the
connective tissue surrounding the prostate (Figure 7).
Explanation of Figures 3 to 6
Figure 3. Cross-section of testis showing seminiferous tubules.
n, nucleus of large cell with no clear cytoplasmic limits.
Figure 4. Seminiferous tubule showing germ cells clustered in
groups in the same maturation phase. spg, spermatogonia; spc,
spermatocytes; spd, spermatids; pcm, polynucleated cellular
masses.
Figure 5. Section of prostate. ie, inner ciliated columnar epithe-
lium; gt, glandular tissue; pl, prostatic lumen.
Figure 6. Duct connecting the lumen of the prostate with the
pallial cavity. gc, goblet cells of the epithelium filled with gran-
ules deeply stained with Phloxine; pl, prostatic lumen; pc, pallial
cavity.
Page 324 The Veliger, Vol. 26, No. 4
Explanation of Figures 7 to 9
Figure 7. Double sheet of epithelium-like cells (line of fusion). Figure 9. Cross-section of penis showing the spermatic duct. ie,
pt, prostatic tissue; pc, pallial cavity. inner epithelium; cm, network of connective tissue and muscle
Figure 8. Cross-section of anterior deferent duct. e, simple cil- fibres oriented in all directions; If, line of fusion; hs, haemal
iated columnar epithelium; If, line of fusion; ee, external epithe- spaces; ee, external epithelium.
lium.
M. Amin V. e¢ al., 1984
Anterior deferent duct
The anterior deferent duct is internally lined with a
simple ciliated columnar epithelium, only slightly invag-
inated (Figure 8). The cytoplasm of the epithelial cells is
granular in the basal portion of the cell and homogeneous
in the apical end; nuclei are small, spherical and centrally
located. The epithelium is underlain by a thin layer of
connective tissue.
All along the length of the duct the double sheet of
epithelium-like cells is observed (Figure 8), which, as it
has been previously described for the prostate, also con-
nects the lumen of the duct with the pallial cavity.
Penis
The penial duct is a straight tube, located laterally
within the organ and internally coated by a simple ciliated
columnar epithelium of various heights (Figure 9). The
cytoplasm of the epithelial cells is homogeneous; nuclei
are oval in shape, basally located, and contain dense gran-
ular chromatin. Goblet cells are seen between epithelial
cells.
The penial duct is surrounded by a mass of tissue com-
posed of a circular muscle layer adhered to the inner ep-
ithelium, and a complex network of connective tissue.
Muscle fibres oriented in all directions, small haemal
spaces, and bundles of nerve fibres intermingle with the
network of connective tissue. Each bundle of nerve fibres
is enveloped by a thin layer of connective tissue. All of
these tissues provide the penis with a compact structure.
The surface of the penis is coated by a simple ciliated
columnar epithelium. The cytoplasm of the columnar cells
is homogeneous, but it is visible only in the apical end,
because the rest of the cell is entirely occupied by a large
fusiform nucleus. Goblet cells are also seen between the
epithelial cells. Also, small basal cells with spherical nu-
clei are observed interspersed with epithelial cells.
All along the penis, and always connecting the sper-
matic duct with the external epithelium, the double sheet
of epithelium-like cells (Figure 9), previously described
for the prostate and the anterior deferent duct, can be
observed again.
The whole structure of the penis exhibits basically the
same histological pattern just described, but the proximal
region of this organ shows a greater abundance of muscle
tissue, gradually decreasing toward the tip of the penis
where connective tissue predominates. The number of
goblet cells in the surface epithelium gradually decreases
from the basal zone to the apical end.
DISCUSSION
The male reproductive system of Chorus giganteus does
not differ from the general pattern described by HOUSTON
(1976), HYMAN (1967), and PURCHON (1977) for the most-
evolved neogastropods. It consists of a testis, seminal ves-
Page 325
icle, posterior deferent duct, prostate, anterior deferent
duct, and penis.
In addition to the germ cells, the seminiferous tubules
contain some larger cells, not clearly delimited, that would
correspond to the basal cells in Colus stumpsoni (Mérch,
1867) as described by WEsT (1978). These cells may play
a nursing role for the differentiation of the germ cells.
Large polynucleated cells, corresponding to gonias that
do not complete cytokinesis during cell divisions, can also
be observed within the seminiferous tubules. This phe-
nomenon was not observed in Concholepas concholepas
(Bruguiere, 1789) (GUZMAN et al., 1972), but it was re-
ported for Colus stimpsoni by WEST (1978).
The first portion of the posterior deferent duct is the
seminal vesicle, which ends in a sphincter muscle. The
occurrence of a seminal vesicle is not a feature common
to all muricids, since in Acanthina angelica I. Oldroyd,
1918, Trophon truncatus (Strom, 1768), and some repre-
sentatives of the genus Thais, the seminal vesicle is absent
(Houston, 1976). However, this structure is found in
Concholepas concholepas (GUZMAN et al., 1972), Trophon
barvicensis (Johnston, 1825), Ceratostoma foliatum (Gme-
lin, 1791) and Urosalpinx cinerea (Say, 1822) (Houston,
1976).
In Chorus giganteus, a segment of the wall of the sper-
matic duct is modified so as to form the prostate, whose
glandular tissue forms a compact mass around the lumen
of the duct; the secretion products are directly poured into
the lumen of the duct. This histological pattern differs
from that of Concholepas concholepas because, in spite of
the fact that in C. concholepas a distinct prostatic gland
occurs, the histology of this gland reveals isolated glan-
dular acini immersed in connective tissue, each one having
its own duct that opens into the spermatic duct (GUZMAN
et al., 1972).
The small, ciliated duct connecting the gland lumen
with the pallial cavity acts in Chorus giganteus as an es-
cape outlet for spermatozoa in case copulation is disturbed
by external factors. Although this arrangement is present
in many higher mesogastropods and neogastropods
(PURCHON, 1977), in Concholepas concholepas, a Chilean
species of the same family and similar geographical dis-
tribution, this connection has not been reported (GUZMAN
et al., 1972).
In the anterior portion of the prostate of Chorus gigan-
teus, the small duct is replaced by a double sheet of epi-
thelium-like cells running along the prostate, the anterior
deferent duct, and the penis. This sheet is also found in
Acanthina, Mitrella, and species of related families, and it
corresponds to the so-called line of fusion of the open
system from less-advanced species. The open system is
found in several species of Littorina, in which the prostate
is composed of two glandular lobes and remains open
throughout its entire length (HOUSTON, 1976).
In Chorus giganteus the penial duct is straight, as in
other genera of the same family, and it is different from
Page 326
that of Concholepas concholepas (GUZMAN et al., 1972) and
that of some species of Thais, Trophon, and Ocenebra
(Houston, 1976) in which the penial duct has been de-
scribed as highly convoluted. Finally, the penial duct is
laterally located within the penis in Chorus giganteus,
whereas in Concholepas concholepas (GUZMAN et al., 1972)
and in Columbella fuscata Sowerby, 1832 (Houston, 1976)
it is centrally positioned.
ACKNOWLEDGMENTS
The authors wish to thank Prof. M. E. Almonacid for his
valuable help in revising the English version of the manu-
script. This work was supported by grant No. 20.31.04
from the Direction of Research, University of Concepcion.
LITERATURE CITED
GALLARDO, C. 1981. Egg masses and hatching stage of the
muricid gastropod Chorus giganteus (Lesson, 1829). Studies
on Neotropical Fauna and Environment 16(1):35-44.
GuZMAN, E., M. AMIN & M. DELPIN. 1972. Aniélisis hist6-
logico del Sistema Reproductor masculino de Concholepas
concholepas (Bruguiere, 1789). Bol. Soc. Biol. Concepcion
45:117-127.
Houston, R. S. 1976. The structure and function of neogas-
The Veliger, Vol. 26, No. 4
tropod reproductive systems: with special reference to Col-
umbella fuscata Sowerby, 1832. Veliger 19(1):27-46.
Humason, G. L. 1967. Animal tissue techniques. 2nd ed. W.
H. Freeman and Company: San Francisco. ix + 569 pp.
Hyman, L. H. 1967. The invertebrates, Vol. 6, Mollusca I.
McGraw-Hill: New York. vii + 792 pp.
LeEpPEZ, I. 1981. Ciclo reproductivo y fecundidad del caracol
Rapana (Chorus) giganteus (Lesson, 1830). Informe final.
Proyecto No. 30807. Convenio Universidad de Concepcién-
Sub-secretaria de Pesca. Mimeografiado.
LILLIE, R. D. 1965. Histopathologic technic and practical his-
tochemistry. 3rd ed. McGraw Hill: New York. xii + 1715
PP-
OLAVE, S. 1981. Determinacién de la fecundidad del caracol
Chorus giganteus (Lesson, 1829) mediante la aplicacién de
una técnica estereométrica. Informe Unidad de Investiga-
cién para optar al grado de Licenciado en Biologia Marina.
Mimeografiado. Depto. de Oceanologia. Universidad de
Concepcion. pp. 1-27.
Osorio, C. 1979. Moluscos marinos de importancia econémica
en Chile. Biologia Pesquera. Chile 11:2-47.
PuRCcHON, R. D. 1977. The biology of the Mollusca. 2nd ed.
Pergamon Press: Oxford. 560 pp.
WEsT, D. L. 1978. Reproductive biology of Colus stimpsoni
(Prosobranchia: Buccinidae). I. Male genital system. Veli-
ger 20(3):266-273.
West, D. L. 1979. Reproductive biology of Colus stimpsoni
(Prosobranchia: Buccinidae). II. Spermiogenesis. Veliger
21(1):1-9.
The Veliger 26(4):327-329 (April 2, 1984)
THE VELIGER —
© CMS, Inc., 1984
Anesthetic Methods for the Moon Snail
Polinices lewisit1
GEORGE B. BOURNE
Bamfield Marine Station, Bamfield, British Columbia, and
Department of Biology, The University of Calgary, Calgary, Alberta T2N 1N4, Canada!
Abstract. Nine chemicals and hypothermia were tested on the moon snail Polinices lewisi for their
effectiveness as anesthetics. Hypothermia and five of the drugs induced anesthesia. Althesin, a mixture
of the steroids alphaxalone and alphadolone acetate, appeared to be the most desirable anesthetic.
Hypothermia and xylazine can also be recommended for routine use. Less favored were ethanol and
sodium pentobarbital. Benzyl alcohol was the most lethal of the compounds tested.
INTRODUCTION
SUCCESSFUL SURGERY, A central requirement for many
physiological studies, often depends on an effective method
of anesthesia. Although anesthetic procedures are well es-
tablished for vertebrates, particularly mammals (GILMAN
et al., 1980), this is not the case with invertebrates despite
the use of invertebrate preparations in studying the neu-
ronal and synaptic activity of many mammalian anes-
thetics (JUDGE, 1980). In the mollusks only a few attempts
have been made to systematically evaluate the effectiveness
of anesthetic procedures (e.g., ANDREWS & TANSEY, 1981
for a cephalopod; RUNHAM et al., 1965, for several gas-
tropods). Although RUNHAM et al. (1965) found several
agents to be effective anesthetics, most of these suffered
the drawback of exceedingly long induction times. This
study, an attempt to update the RUNHAM et al. (1965)
investigation, details the search for an effective, quick-
acting anesthetic for the moon snail Polinices lewisi (Gould,
1847).
MATERIALS anp METHODS
The moon snails used in this study ranged in wet weight
from 75 to 160 g; animals were weighed in the retracted
state. All animals, collected in Barkley Sound, Vancouver
Island, were held for at least five days in running seawater
at 31 to 32%o salinity and 10 to 12°C before experimen-
tation was commenced. The holding tank was provided
with a fine sandy bottom.
The anesthetic methods tried can be divided into two
‘Requests for reprints should be sent to the University of
Calgary address.
categories: physical and chemical. In the physical method,
hypothermia, an animal was placed in a seawater bath
and the bath temperature dropped to 2°C over a one-hour
period. In the chemical methods, the following agents were
tried: Althesin (Galaxo Laboratories), benzyl! alcohol, car-
bon dioxide, ethanol, magnesium chloride, MS 222 (Sig-
ma), quinaldine, sodium pentobarbital (Somnotol-MTC
Pharmaceuticals), and xylazine (Rompun-Cutter Labo-
ratories). To obtain estimates of initial anesthetic concen-
trations, the following sources were consulted: BELL (1964),
RUNHAM et al. (1965), and the manufacturers’ literature.
At ambient seawater temperature, anesthesia with
chemicals was conducted on an expanded animal placed
in one liter of seawater in a glass dish of 20 cm diameter
and 7 cm height. Liquid chemicals then were added slowly
to the bath, with mixing accomplished by a peristaltic
pump. Carbon dioxide simply was bubbled into the bath.
The behavior of an animal was visually monitored dur-
ing the induction. Generally the signs noted were as fol-
lows: (1) hyperactivity, unusual crawling or extreme ex-
pansion of the foot and mantle; (2) retraction responses,
either of the whole or parts of the animal; (3) lack of
responsiveness to a water jet and touch of a stainless steel
probe; and (4) flaccid expansion, especially of the tenta-
cles.
If induction was successful the animal was allowed to
recover in running seawater, after which the amount of
anesthetic was calculated. Each chemical was given six
individual animal trials; for the successful ones a second
phase of testing occurred in an attempt to establish the
minimum concentration needed. This was accomplished
by testing at one half the initial concentration and then
again at added 10% increments.
After establishing the minimum concentration, a new
Page 328
Table 1
Summary of anesthetic actions on the moon snail
Polinices lewirsit.
% re- % sur-
Concetmcan Induc- tracted vival?
No. of tion during after
ani- (ug/ time sur- 1
Anesthetic mals (%) mL) (h) gery' week
Althesin 18 0.15 14° 2 22 93
Benzyl alcohol 10 0.5-1 — >1 0 10
Ethanol 15 4 — 3 47 V5)
Sodium pento- 10 0.14 91 2.5 20 38
barbital
Xylazine 20 0.06 12 2.5 35 62
Cold (2°C) 8 — —_— 1.5 50 100
‘Surgery lasted 0.5 h.
? Retracted animals eliminated.
> This is the final concentration of alphaxalone, one of two
active ingredients in Althesin. The commercially available prep-
aration of Althesin contains alphaxalone (9 mg/mL) and alpha-
dolone acetate (3 mg/mL). The latter compound, although pos-
sessing some anesthetic activity in humans, is added to increase
the solubility of the mixture (REYNOLDS & PRASAD, 1982).
batch of animals subjected to the successful anesthetics
underwent surgery. This operation consisted of cutting a
hole of 0.5-mm diameter in the dorsal part of the shell
and another of 4-mm diameter in the left ventral part of
the shell in order to implant impedance-conversion elec-
trodes. A Biocom impedance converter coupled to a Gould
recorder was used to make recordings of body movements
during the early recovery phase; total recovery of these
animals was monitored for at least one week.
(A)
(B)
The Veliger, Vol. 26, No. 4
RESULTS
For various reasons the following substances were rejected
as anesthetics for moon snails: carbon dioxide (up to sat-
uration), magnesium chloride (2.4%), MS 222 (1 mg/mL)
and quinaldine (saturated solution). Carbon dioxide and
magnesium chloride both failed to induce anesthesia with-
in four hours. However, MS 222 and quinaldine ap-
peared to be highly noxious and caused the moon snails
to retract into the shell. Once retracted the moon snails
did not extend while immersed in the solutions containing
MS 222 and quinaldine.
All other chemicals and hypothermia induced varying
states of anesthesia. Table 1 summarizes the results of the
second-phase testing of those agents. Exactly when the
effects of the agents wore off was difficult to ascertain;
therefore, the percentage of animals that retracted during
surgery was used as the comparative indicator of that fac-
tor.
The behavior of animals during recovery was variable
and depended on the anesthetic used. Moon snails that
were recovering from cold exposure and ethanol immer-
sion remained quiet for one to two hours after being placed
in running seawater, after which the animals tended to
crawl around the recovery tank for several hours. How-
ever, with Althesin, benzyl alcohol, and xylazine, the
quiescent period was more extensive and lasted as long as
a day. During the longer quiescent periods many of the
animals turned upside down, but this behavior was also
observed in normal animals both in the wild and in cap-
tivity.
Impedance recordings of body movement within the shell
revealed that the quiescent period masked other aspects of
the recovery (Figure 1). In all instances body movements
ics dal cea huchoninaldsa( Secs leneib dawned a donde
10 min
Figure 1
Impedance recording of body movements within the shell of a specimen of Polinices lewisi following Althesin
anesthesia. (A): early recovery period—the arrow indicates the onset of the body movements, which in this instance
occurred approximately 1.2 h after the animal was placed in running seawater to recover. (B): fully recovered
animal—the recording was made while the animal was crawling and occurred 40.7 h after the animal was in
running seawater. Unlike the previous recording (A), the predominant activity in (B) is the beating of the heart
upon which is superimposed other body movements.
G. B. Bourne, 1984
occurred within the shell with no apparent external body
conformational changes. The earliest onset of these inter-
nal body movements followed cold exposure and Althesin
immersion, with benzyl alcohol delaying the movements
longest.
Table 1 also demonstrates that benzyl alcohol was the
most lethal of the chemicals, inducing such visible signs
of distress as the sloughing off of an animal’s epidermis
and pigment within two days. Deaths from the other agents
gave no such outward indication.
DISCUSSION
The results of this study demonstrate that anesthesia of
the moon snail Polinices lewis can be accomplished by
immersion in solutions of anesthetic agents. Because a
primary requirement of the study was to ensure that an-
imals remained expanded, no attempt was made to inject
anesthetics. In this regard, there was also a practical con-
sideration of finding a blood space within the voluminous
aquiferous system, for BERNARD (1968) has shown that
system to contain a volume of water equal to 50% of the
total weight.
This study also revealed several well-known aquatic
vertebrate anesthetics, carbon dioxide, MS 222, and quin-
aldine (BELL, 1964), to be ineffective for moon snails. For
MS 222 and quinaldine the problem appeared to be their
highly noxious nature, which caused animals to retract
into the shell. However, rejection of carbon dioxide was
based on its failure to induce anesthesia after four hours.
Like carbon dioxide, magnesium chloride was also re-
jected for its inability to cause anesthesia within a reason-
able time. In the Mollusca, as in many invertebrates, mag-
nesium chloride is most widely used as a narcotizing agent
(RUNHAM et al., 1965). Runham and his colleagues, em-
ploying magnesium chloride to anesthetize the marine
prosobranchs Littorina littorea and Nucella lapillus, found
that it took overnight to accomplish the task.
Hypothermia appears to be a reasonable means of an-
esthesia when the surgical procedures are simple. ANDREWS
& TANSEY (1981) indicated that hypothermia is a desir-
able method in Octopus, especially for neuropharmaco-
logical experiments.
Of the several chemicals, Althesin appears to be the
optimal agent for use in the moon snail. It possesses sev-
eral acceptable characteristics: low lethality, comparative-
ly short induction time, and relatively quick recovery time.
Alphaxalone, the major active ingredient of Althesin, has
been injected into the crabs Carcinus maenas and Cancer
pagurus to bring about a “sleep time” of two to three hours
(OSWALD, 1977). In the moon snail the “sleep time”’ fol-
Page 329
lowing Althesin anesthesia appears to be similar to that
of crabs subjected to alphaxalone.
Xylazine ranks as the second chemical of choice, pos-
sessing a higher lethality than Althesin. OSWALD (1977)
found xylazine to be a desirable, fast-acting anesthetic for
crabs.
Ethanol and sodium pentobarbital could be used, but
have little to offer in preference to Althesin and xylazine.
Obviously if cost and availability are factors, then ethanol
can be considered. The lethal nature of benzyl alcohol
makes it wholly undesirable as an anesthetic in moon
snails.
No attempt was made in this study to elucidate the
mode of action of any of the chemicals. It is tempting to
speculate that the drugs Althesin and xylazine were ex-
erting a central action. However, more study is needed to
confirm this as well as to understand the site of entry,
distribution, and breakdown of these drugs. Althesin and
xylazine should be tested in other gastropod species to see
whether they may serve as general anesthetics for snails.
ACKNOWLEDGMENTS
I thank Dr. R. E. Foreman, Director of the Bamfield
Marine Station, and his staff for the many kindnesses
shown during my stay at the station. In particular, exten-
sive thanks go to Ms. Sabina Leader for help in collecting
and maintaining animals. I also thank Dr. S. H. Roth for
bringing Althesin to my attention.
LITERATURE CITED
ANDREWS, P. L. R. & E. M. Tansey. 1981. The effects of
some anaesthetic agents in Octopus vulgaris. Comp. Bio-
chem. Physiol. 70C:241-247.
BELL, G. R. 1964. A guide to the properties, characteristics,
and uses of some general anaesthetics for fish. 2nd ed. re-
vised. Bull. Fish. Res. Board Can. 148: 7 pp.
BERNARD, F.R. 1968. The aquiferous sytem of Polinices lewisii
(Gastropoda, Prosobranchiata). J. Fish Res. Board Can. 25:
541-546.
GitmaNn, A. G., L. S. GOODMAN, A. GILMAN, S. E. MAYER &
K. L. MELMEN, EDs. 1980. The pharmacological basis of
therapeutics. 6th ed. Macmillan Publishing Co.: New York.
JupbcE, S. E. 1980. General anaesthetic action in the inverte-
brate central nervous system. Gen. Pharmacol. 11:337-341.
OswaLp, R. L. 1977. Immobilization of decapod Crustacea for
experimental procedures. J. Mar. Biol. Assoc. U.K. 57:715-
721.
REYNOLDS, J. E. F. & A. B. PRASAD, EDS. 1982. Martindale.
The extra pharmacopoeia. 28th ed. The Pharmaceutical
Press. London.
RunNHAM, N. W., K. ISARANKURA & B. J. SMITH. 1965. Meth-
ods for narcotizing and anaesthetizing gastropods. Malaco-
logia 2:231-238.
The Veliger 26(4):330-331 (April 2, 1984)
THE VELIGER
© CMS, Inc., 1984
NOTES, INFORMATION & NEWS
An Earlier Name for Nassarius corpulentus
(C. B. Adams, 1852)
by
Richard E. Petit
806 St. Charles Rd.,
North Myrtle Beach, South Carolina 29582
Examination of type specimens of Cancellariidae in the
Muséum National d’Histoire Naturelle, Paris, has re-
vealed that Cancellaria nassiformis Lesson, 1842:204, is not
cancellariid but is the species later described as Nassa
corpulenta C. B. Adams, 1852:284. The type lot of Can-
cellaria nassiformis Lesson consists of seven syntypes from
Acapulco, Mexico, the only locality cited by Lesson.
As Lesson’s name has ten years’ priority over the one
proposed by C. B. Adams, it must either be employed as
the correct name or it must be rejected by action of the
International Commission on Zoological Nomenclature.
This note is being published to call this matter to the
attention of systematists interested in the Panamic-Pacific
Nassariidae who can better judge which course of action
should be followed.
The writer is indebted to Dr. Philippe Bouchet, Cu-
rator of Marine Mollusks, Muséum National d’ Histoire
Naturelle, Paris, who not only made the type material
available for study, but also provided bibliographic infor-
mation. Appreciation is also expressed to Dr. James H.
McLean, Los Angeles County Museum of Natural His-
tory, Los Angeles, for examining some of these syntypes
and confirming their conspecificity with Nassarius corpu-
lentus (C. B. Adams).
Literature Cited
ADAMS, C. B. 1852. Catalogue of shells collected at Panama
with notes on synonymy, station and habitat. Ann. Lyceum
Natur. Hist. New York 5:222-549.
Lesson, R. P. 1842. Notes sur quelques Mollusques rares ou
nouveaux recueillis dans la Mer du Sud, par M. Adolphe
Lesson. Actes Soc. Linn. Bordeaux 12:203-209.
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The Veliger 26(4):332-334 (April 2, 1984)
THE VELIGER
© CMS, Inc., 1984
BOOKS, PERIODICALS & PAMPHLETS
Mollusca
by KENNETH J. Boss. 1982. Pp. 945-1166 in Vol. 1 and
pp. 1092-1096 in Vol. 2. In: Sybil P. Parker (editor-in-
chief), Synopsis and classification of living organisms.
McGraw Hill: New York. 2 vols. $150.
Here is a significant work that should be at hand in
every malacological laboratory. It is a detailed review down
to the family and subfamily level of all living mollusks.
Information about shell and anatomical morphology is
presented, together with notes on distribution and a few
key references. This is the first attempt to provide such a
detailed overview since Thiele’s Handbuch der Systemati-
schen Weichtierkunde (1929-1935). It will provide both a
handy reference for students of malacology and a stimulus
to workers to fill in the significant gaps that exist in our
knowledge of many molluscan groups.
Workers familiar with the literature on particular fam-
ilies will, of course, see that key points are missing and
that there are misinterpretations. In a work of this mag-
nitude, this is unavoidable, and its author is already so-
liciting comments for a proposed second, more-detailed
edition, with far more illustrations (included to help define
some of the terms used) than the few of this edition. One
may hope that the Mollusca section by itself will be avail-
able separately by then so that specialists will not have to
purchase the entire two-volume work.
It takes particular dedication and persistence to com-
plete the important compilations that lay the groundwork
for future contributions. Few have the stamina to attempt
them and to avoid the distractions that the inadequacies
in our knowledge and the contractions in the available
literature present in virtually every group. Kenneth Boss
deserves a great deal of credit for completing this task and
for resolving to build on it as well.
Eugene Coan
Catalogue of the Living Bivalvia of the Eastern
Pacific Ocean: Bering Strait to Cape Horn
by F. R. BERNARD. 1983. Canadian Special Publication
of Fisheries and Aquatic Sciences 61, 102 pp. Price $8.00
(Canadian) in Canada, $9.60 elsewhere.
Students of any fauna are fortunate when there exists
a checklist or catalogue listing all the described or recog-
nized taxa in their special area—more so when data on
geographic, geologic, and depth distribution are included.
This work consists of a systematic catalogue and a bibli-
ography of the primary descriptive literature on the living
bivalves of a geographic swath 2000 km wide extending
from the Bering Strait (66°N) to Cape Horn (60°S), along
with an impressive array of data concerning “where, when,
and how deep.”
Like other works of equivalent scope, this one takes a
few risks. Checklists do not readily admit multiple work-
ing hypotheses, and every taxonomist carries in his head
numerous cases where the only proper systematic readout
must be “‘wait and see.” Moreover, the coverage is vast—
several geographic provinces and 1308 species. With the
unprecedented number of biologists now concerned with
bivalves and (at least peripherally) bivalve systematics,
there are bound to be disagreements regarding form and
content.
Each species entry includes a reference to the original
description, and the same information for taxa regarded
as synonyms. There are many nomenclatural innovations,
mainly at the family, subfamily, and superfamily levels;
an essay on the classification of Bivalvia gives the back-
ground on some of Bernard’s taxonomic choices.
The geographic list continues the practice, originally
proposed by SCHENCK & KEEN (1937) and implemented
in KEEN’s (1938) checklist, of giving the midpoint-of-range,
the arithmetic mean of the north and south limits of dis-
tribution. Apparently a forthcoming paper by Bernard
and another author will discuss the use of midpoint-of-
range analysis. The method has found limited acceptance
for the interpretation of paleoclimates. ALLISON’s (1973)
summary criticisms are perhaps the most cogent.
The depth ranges are said to include no depths based
on dead and probably displaced material; this must have
required some fine judgment as to which material was
displaced and which was not.
A temperature range is given for each species, in “an
attempt to supply another index useful for estimating pa-
leotemperatures of Pleistocene bivalve faunas” (p. 2). Al-
though it is stated that the computer-calculated value is
the mean of the closest adjoining records, the statistic is
nowhere defined. Are these mean annual temperatures?
Mean maximum summer temperatures in the warm part
of the range and mean minimum winter temperatures in
the cold part? Historical maxima and minima? Or some
other thermal measure? At depth, seasonal variation may
not amount to much, but in shallow waters it can be
considerable. For animals with seasonal cycles, the lowest
(or highest) temperature at a particular time of year may
be critical, the mean annual temperature hardly impor-
tant. I cannot see using the Bernard figures as any sort of
index without knowing for what they stand.
This part of the text speaks also of analysis using “the
proportion of thermophilic and cryophilic species” (al-
though it is not the proportion of thermophilics and cryo-
philics that indicates a minimal temperature range, as the
text has it). Applied with caution, this is a useful type of
Books, Periodicals & Pamphlets
paleoclimatic analysis; it would have been helpful to cite
examples and explanations of the technique, perhaps
VALENTINE & MEADE (1961) or LINDBERG et al. (1980).
The geologic range information consists of the epoch
name for the oldest known occurrence in the eastern Pa-
cific. The standard is said to be the Pacific coast provincial
megafossil chronology—as though there were one stan-
dard, or even one province, applicable from the Bering
Sea to Cape Horn. No bibliographic reference is cited.
The expression “Pacific coast provincial standard” has
often been used to refer to the correlation chart of WEAVER
et al. (1944), but the coverage of that work stops south of
Alaska and north of the present-day tropical realm. The
last 5-10 years have seen important revisions in the age
assignments of tropical American Cenozoic sections. Most
current biostratigraphy around the northeastern Pacific
rim attempts to relate ages to the European series-epoch
standard, and trans-Pacific correlations proceed on this
basis as well. There is a strong current trend toward the
use of regionally defined stages (e.g., ADDICOTT, 1976)
rather than epochs to classify the faunal succession in the
provinces of the eastern Pacific. For these reasons, the
epoch citations in the catalogue have limited utility.
Users need to double-check the epoch records anyway:
Glycymeris vancouverensis Clark & Arnold, 1923, de-
scribed from the Juanian Stage (earliest Miocene) Sooke
Formation, appears under the synonymy of G. corteziana
Dall, 1916, but only the age “Recent” is given.
It may come as a surprise that Bernard has chosen not
to use the category of subspecies, even though “the ma-
jority of wide-ranging species are expected to yield several
subspecies” (p. 1). As a heuristic device, this stance might
be defensible. The criteria for recognizing a subspecies
are, or ought to be, more restrictive than those for a species
and the relevant tests have rarely been applied. Unfortu-
nately, the treatment of taxa formerly regarded as sub-
species is inconsistent and apparently subjective, some being
synonymized and others showing up at the species rank.
A few typographic conventions are unfortunate. For
instance, the centered geographic notes (“South Atlantic,”
“Arctic Ocean”) stand out unnecessarily, while family,
superfamily, and higher category names, at the left mar-
gin, recede into the background. Somewhat more serious
are the numerous uncorrected typographic errors in the
explanatory text—not because they themselves are con-
fusing, but because they suggest that the catalogue itself
may also fall short on accuracy. My response runs from
the (probably pedantic) concern that some of the Latin
names may not have been transcribed correctly (Is it Ru-
diphaga Olsson, 1961, or Rupiphaga?) to the fear that
some of the depth or latitude citations may be flat-out
erroneous because of typos.
Some overdue housecleaning disposes (by the best evi-
dence possible) of the “questionables”—e.g., Pteria viri-
dizona—but it is also good that they remain in small type
in the body of the list. The notes (pp. 67-70) are inter-
esting for showing the many ways in which spurious rec-
Ragemo>
ords can become entrenched in the literature. More “‘ques-
tionables” are bound to turn up; in other cases, it may be
too early to write some of them off. For example, even if
Vulsella pacifica (Dall, 1916) from Nicagarua is synony-
mous with the Indo-Pacific V. mytilina (Lamarck, 1819),
might it not be another of the many cases of Indo-Pacific
faunal elements present in the eastern Pacific, rather than
malacologist error?
Not surprisingly, some familiar names get changed. In
my opinion, demotion of Hinnites Defrance, 1821, to a
subgenus of Chlamys Roding, 1798, may not go far enough,
because late cementation and opportunistic, irregular
growth have evidently arisen independently many times.
Kellia laperousu (Deshayes, 1839) falls as a synonym of
K. suborbicularis (Montagu, 1803), not unexpectedly, but
one awaits the documentation.
The name Panope abrupta (Conrad, 1849) is used for
the large, common bivalve of the northern Pacific usually
known as Panope (or Panopea) generosa Gould, 1851. Mya
abrupta Conrad, 1849, was rejected by early workers as a
junior secondary homonym in the genus Panopea, and the
junior name P. generosa used instead. Moore (1963) re-
stored the name P. abrupta on the grounds that Pholado-
mya abrupta Conrad, 1832, is not a Panopea, as it had
been considered by previous workers. Under the current
ICZN rules, however (“A junior secondary homonym re-
jected before 1961 is permanently rejected . . .”—Article
59[b][1]), the name Panopea generosa should stand. Ac-
cording to Bernard, the northwestern Pacific Panopea ja-
ponica (A. Adams, 1850) is indistinguishable from the
American species; in this case, P. japonica is the earliest
available name. Workers in the state of Washington, where
this clam is something of a cultural hero, will undoubtedly
be distressed.
I hope most users of Bernard’s catalogue will recognize
that many of the assertions, synonymies, and taxonomic
rankings are not yet rigorously demonstrated. The work
is a better statement of the way things might be than we
have had before. In its innovations, it calls upon thought-
ful systematists to examine the evidence behind their own
assumptions. That can be a disquieting experience, but as
my systematics coach might say, “‘no pain, no gain!”
Literature Cited
AppDIcoTT, W. O. 1976. Neogene molluscan stages of Oregon
and Washington. Soc. Econ. Paleontol. Mineralog., Pacific
Sec., Neogene Sympos.: pp. 95-115.
ALLISON, R. C. 1973. Marine paleoclimatology and paleo-
ecology of a Pleistocene invertebrate fauna from Amchitka
Island, Aleutian Islands, Alaska. Palaeogeog. Palaeoclima-
tol. Palaeoecol. 13:15-48.
KEEN, A. M. 1938. An abridged check list and bibliography
of west North American marine Mollusca. Stanford Univ.
Press: Stanford, Calif. 87 pp.
LINDBERG, D. R., B. RoTH, M. G. KELLoGG & C. L. Husss.
1980. Invertebrate megafossils of Pleistocene (Sangamon
Interglacial) age from Isla de Guadalupe, Baja California,
Mexico. Pp. 41-62. In: D. M. Power (ed.), The California
Page 334
The Veliger, Vol. 26, No. 4
Islands: Proceedings of a multidisciplinary symposium. San-
ta Barbara Mus. Natur. Hist., Santa Barbara, Calif.
Moore, E. J. 1963. Miocene marine mollusks from the As-
toria Formation in Oregon. U.S. Geol. Surv. Prof. Pap. 419:
109 pp.
SCHENCK, H. G. & A. M. KEEN. 1937. An index method for
comparing molluscan faunules. Proc. Amer. Philos. Soc. 77:
161-182.
VALENTINE, J. W. & R. F. MEADE. 1961. Californian Pleis-
tocene paleotemperatures. Univ. California Publ. Geol. Sci.
40:1-46.
WEAVER, C. E. et al. 1944. Correlation of the marine Ce-
nozoic formations of western North America. Bull. Geol.
Soc. America 55:569-598.
Barry Roth
Fauna and Hydrobiology of the Shelf
Zones of the Pacific Ocean
Proceedings of the XIV Pacific Science Congress (Kha-
barovsk, August 1979). Edited by O. G. Kussakin and A.
I. Kafanov. Far East Science Center, Academy of Sciences
of the USSR, Vladivostok, 148 pp. Price 1r 70k (about
$2.00 US) [in Russian with English summaries].
Of the 20 papers published in this volume from the
marine biology section meeting, 9 treat mollusks or faunas
that are predominantly molluscan. These papers cover a
broad range of topics including ecology, paleontology, and
biogeography.
A. J. Kohn combines paleontology with ecology and
presents a preliminary report on the evolution of the Indo-
Pacific Conidae. Ecological work in the North Pacific in-
cludes investigations of Mytilus edulis communities in the
Sea of Okhotsk by V. G. Averincev et al., as well as a
study of subtidal communities to a depth of 200 m along
the east coast of Kamchatka by A. N. Golikov and O. A.
Scarlato. From the South Pacific, E. W. Dawson presents
distribution patterns for bathyal mollusks on the Camp-
bell Plateau and Chatham Rise.
In the biogeographic realm, K. Y. Arakawa discusses
the biogeography and ecology of sedentary invertebrates
including three species of mollusks introduced into Jap-
anese waters. On larger scales, K. N. Nesis examines the
distribution of cephalopods in the Pacific Ocean and pro-
poses zoogeographic provinces based on these distributions
that are in turn compared to shelf provinces. J. C. Briggs
establishes criteria for recognizing centers of origin and
concludes that the central East Indies and the North Pa-
cific Ocean have been important centers of origin for ma-
rine shelf faunas. Another dispersal view is presented by
M. Horikoshi who examines larval transport, endemism,
and reproductive mode of shelf and island faunas in the
Pacific Ocean. A. I. Kafanov adds the indigenous species’
competitive abilities to the dispersal model and examines
the evolution of North Pacific molluscan faunas.
Because of the variety of topics, this proceedings volume
and the individual papers that it contains will be of in-
terest to many workers who study past and present North
Pacific mollusks and their ways. Because the papers are
written in Russian, let us hope that information regarding
the existence of any English versions is forthcoming.
D. R. Lindberg
Information for Contributors
Manuscripts
Manuscripts must be typed on white paper, 812” by 11”, and double-spaced throughout
(including references, figure legends, footnotes, and tables). To facilitate the review pro-
cess, manuscripts, including figures, should be submitted in triplicate. The first mention
in the text of the scientific name of a species should be accompanied by the taxonomic
authority, including the year, if possible. Underline scientific names and other words to
be printed in italics. Metric and Celsius units are to be used.
The sequence of manuscript components should be as follows in most cases: title page,
abstract, introduction, materials and methods, results, discussion, acknowledgments, lit-
erature cited, figure legends, figures, footnotes, and tables. The title page should be on a
separate sheet and should include the title, author’s name, and address. The abstract
should describe in the briefest possible way (normally less than 200 words) the scope,
main results, and conclusions of the paper.
Literature cited
References in the text should be given by the name of the author(s) followed by the
date of publication: for one author (SMITH, 1951), for two authors (SMITH & JONES,
1952), and for more than two (SMITH et al., 1953).
The “literature cited” section must include all (but not additional) references quoted
in the text. References should be listed in alphabetical order and typed on sheets separate
from the text. Each citation must be complete and in the following form:
a) Periodicals
Cate, J. M. 1962. On the identifications of five Pacific Mitra. Veliger 4:132-134.
b) Books
Yonge, C. M. & T. E. Thompson. 1976. Living marine molluscs. Collins: London.
288 pp.
c) Composite works
Feder, H. M. 1980. Asteroidea: the sea stars. Pp. 117-135. In: R. H. Morris, D. P.
Abbott & E. C. Haderlie (eds.), Intertidal invertebrates of California. Stanford Univ.
Press: Stanford, Calif.
Tables
Tables must be numbered and each typed on a separate sheet. Each table should be
headed by a brief legend.
Figures and plates
Figures must be carefully prepared and should be submitted ready for publication.
Each should have a short legend, listed on a sheet following the tables.
Text figures should be in black ink and completely lettered. Keep in mind page format
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Photographs for half-tone plates must be of good quality. They should be trimmed off
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and that lettering size is appropriate to the figure. Charges will be made for necessary
alterations.
Processing of manuscripts
Receipt of a submitted manuscript, except in the case of foreign authors, is not ac-
knowledged unless a stamped, self-addressed envelope is enclosed. Upon receipt each
manuscript is critically evaluated by at least two referees. Based on these evaluations the
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Send manuscripts, proofs, and correspondence regarding editorial matters to: Dr. David W.
Phillips, Editor, 2410 Oakenshield Road, Davis, CA 95616 USA.
CONTENTS — Continued
Reproductive cycle of Anomia simplex (Pelecypoda: Anomiidae) from Cape Cod,
Massachusetts.
DIANE J. BROUSSEAU) 64.)¢ nt Se Dd eae ee ime pain nat Scan aS lee 299
Influence of varying oxygen tension on the oxygen consumption of the freshwater
mussel Lamellidens marginalis (Lamarck) and its relation to body size.
V. MaDAN MOHAN Das AND S. A. T. VENKATACHARI ................. 305
Gaimardia bahamondei, spec. nov., from central Chile (Mollusca: Bivalvia: Cy-
amiidae: Gaimardiinae).
CECIEIAVTOSORIONRE AND) RAGRICK@NIREARINA WD neuen ene net ya Sel
Egg masses and larvae of three species of Cerithium from the Arabian Sea.
S OHVATIEY ByAIRIK ACIP AINIID N/T) Z/ANWANNATIING 7 NUTONE) Je ee st oe ee 316
Male reproductive system of Chorus giganteus (Lesson, 1829) (Muricidae: Proso-
branchia): anatomical and histological description.
MartTA AMIN V., IRENE LEPEZ G., OSCAR MARIN S., AND MayA DELPIN A.
sheng tbl ela RAE) ala. ata au Lea ead te am aE RO ek Se ac am.... 320
Anesthetic methods for the moon snail Polinices lewisit.
GEORGE BY BOURNE! 10 2 Ie RE TORT el Vesa CATE cla Ree gl By 7)
NOTES, INFORMATION & NEWS
An earlier name for Nassarius corpulentus (C. B. Adams, 1852).
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